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Archive of Story of Palaeobotany Ser. 196-199
livingfossil 2013-9-19 04:24
Archive of Story of Palaeobotany Series 196-199 古植物学的故事( 196 ): 古植物学博士:毕业就业愁断肠,改行改志放眼量 Story of Palaeobotany Series (No.196) Chinese palaeobotany students with lots of worry for study and jobs (in Chinese) http://blog.sciencenet.cn/blog-225931-686785.html archive of story of-palaeobotany-ser-196.pdf ----------- 古植物学的故事 ( 第 197 期 ) 《英国专辑》 ( 补充之一 ) 我所认识的第一位英国古植物学家 -- Dianne Edwards ( FRS, 1942-- ) Story of Palaeobotany Series (197) Dianne Edwards (FRS, 1942--), the first British palaeobotanist I have known (The 1 st Addendum to the Special Issue for British Palaeobotany) http://blog.sciencenet.cn/blog-225931-691304.html archive of story of palaeobotany ser-197.pdf -------- 古植物学的故事(第 198 期) 关于中国的古植物学术社团(之九) 中国植物学会古植物学分会怎么办? Story of Palaeobotany Series (No.198) Palaeobotanical community in China Two state-run palaeobotanical associations in China (partIX) Where is the Palaeobotanical Association of Botanical Society of China (BSC) going next? http://blog.sciencenet.cn/blog-225931-697567.html archive of story of palaeobotany ser-198.pdf ----- 古植物学的故事 199 期 以古植物学为例谈建立中国国家自然历史博物馆的必要性与紧迫性(提纲) http://blog.sciencenet.cn/blog-225931-702778.html Story of Palaeobotany Series (No.199) How to promote the rapid rise of Chinese palaeobotany in the round? (Part XVIII) Palaeobotany is employed to illustrate the necessity and urgency of establishing the National Museum of Natural History of China (NMNHC) archive of story of palaeobotany ser-199.pdf ================ Refer to the catalogue: The bilingual Catalogue of the Story of Paeobotany Series (Issues 0 to199) http://blog.sciencenet.cn/blog-225931-708772.html 2013-7-1707:27
个人分类: 《古植物学的故事》档案Archive of SPS|2530 次阅读|0 个评论
[转载]Urban Studies Foundation Seminar Series 2013(£20,000)
geog 2013-8-28 18:43
Dear Colleague The Urban Studies Foundation is pleased to announce its Seminar Series Competition, which aims to support the generation of internationally excellent research in all areas of urban studies. In the 2013 competition, we seek to support up to three seminar series, in each case up to a maximum of £20,000. Applications to the Competition will be received in two stages and initial applications should be submitted no later than 1 November 2013. We welcome proposals from academics working in any country and all proposals should be clearly international in coverage and scope. Proposals should be in-scope in relation to the interests of the Urban Studies Journal academic community. Further information and the short Initial Application Form are available to download at the Foundation’s website at www.urbanstudiesfoundation.org and enquiries should be made to Ruth Harkin (ruth.harkin@glasgow.ac.uk) in the first instance. Yours sincerely, Professor Joanne Sharp Director Urban Studies Foundation Urban Studies Foundation is a registered charity, reference number SC039937
1891 次阅读|0 个评论
Reading Time Series Plots Reference Key
xiaoxinghe 2013-4-4 11:15
ReadingTimeSeriesPlotsReferenceKey.pdf
个人分类: Time series|1 次阅读|0 个评论
[转载]Introduction to Reading GPS Time Series Plots
xiaoxinghe 2013-4-4 10:40
Introduction to Reading GPS Time Series Plots http://cws.unavco.org:8080/cws/modules/readingGPStimeseries This activity provides a brief introduction to GPS and provides a student activity to practice creating and reading time series plots with simplified GPS data. Students graph how a tectonic plate (and the GPS unit attached to it) has moved over a five year time period by moving a GPS model across a North-East coordinate graph. The following files are needed to complete this activity: Introduction to Reading GPS Time Series Plots (v. May 2011) This presentation provides a brief overview of how GPS can be used to study plate motion, earthquakes, and seismic waves using the Mw=9.0 Tohoku, Japan Earthquake as an example; a brief summary of the development of thought about the shape of the Earth and Geodesy, how GPS works, and step by step how to read GPS time series plots, a brief assessment of learning, and practice with a simple dataset with Iceland as an example. Student Worksheet Reading Time Series Plots (v. May 2011) ; in Spanish v. 2008 Tenths of a Year to Months of a Year Scale Reading Time Series Plots Reference Key ; in Spanish Teacher Guide and Answer Key (v. May 2011) ; After this activity, students explore authentic GPS data; see: Exploring Plate Motion and Deformation in California Using GPS Time Series Plots Using GPS data to visualize plate tectonics in the Pacific Northwest Real GPS Data: Surprising Discoveries in Iceland Additional Resources: The activity: Introduction to Reading Time Series Plots and activity: Exploring Plate Motion and Deformation in California Using GPS Time Series Plots have been tied together in a single Lesson Plan (v.June 2008) This lesson plan also includes an answer key. Draft Versions of this activity
个人分类: Time series|2 次阅读|0 个评论
Using R for Time Series Analysis
xiaoxinghe 2013-4-4 10:31
http://a-little-book-of-r-for-time-series.readthedocs.org/en/latest/src/timeseries.html#plotting-time-series http://a-little-book-of-r-for-biomedical-statistics.readthedocs.org/en/latest/#welcome-to-a-little-book-of-r-for-biomedical-statistics Welcome to a Little Book of R for Multivariate Analysis! ¶ By Avril Coghlan , Wellcome Trust Sanger Institute, Cambridge, U.K. Email: alc@sanger.ac.uk This is a simple introduction to multivariate analysis using the R statistics software. There is a pdf version of this booklet available at: https://media.readthedocs.org/pdf/little-book-of-r-for-multivariate-analysis/latest/little-book-of-r-for-multivariate-analysis.pdf . If you like this booklet, you may also like to check out my booklet on using R for biomedical statistics, http://a-little-book-of-r-for-biomedical-statistics.readthedocs.org/ , and my booklet on using R for time series analysis, http://a-little-book-of-r-for-time-series.readthedocs.org/ . Contents: How to install R Introduction to R Installing R How to check if R is installed on a Windows PC Finding out what is the latest version of R Installing R on a Windows PC How to install R on non-Windows computers (eg. Macintosh or Linux computers) Installing R packages How to install an R package How to install a Bioconductor R package Running R A brief introduction to R Links and Further Reading Acknowledgements Contact License Using R for Multivariate Analysis Multivariate Analysis Reading Multivariate Analysis Data into R Plotting Multivariate Data A Matrix Scatterplot A Scatterplot with the Data Points Labelled by their Group A Profile Plot Calculating Summary Statistics for Multivariate Data Means and Variances Per Group Between-groups Variance and Within-groups Variance for a Variable Between-groups Covariance and Within-groups Covariance for Two Variables Calculating Correlations for Multivariate Data Standardising Variables Principal Component Analysis Deciding How Many Principal Components to Retain Loadings for the Principal Components Scatterplots of the Principal Components Linear Discriminant Analysis Loadings for the Discriminant Functions Separation Achieved by the Discriminant Functions A Stacked Histogram of the LDA Values Scatterplots of the Discriminant Functions Allocation Rules and Misclassification Rate Links and Further Reading Acknowledgements Contact License Acknowledgements Thank you to Noel O’Boyle for helping in using Sphinx, http://sphinx.pocoo.org , to create this document, and github, https://github.com/ , to store different versions of the document as I was writing it, and readthedocs, http://readthedocs.org/ , to build and distribute this document. Contact I will be very grateful if you will send me ( Avril Coghlan ) corrections or suggestions for improvements to my email address alc@sanger.ac.uk License The content in this book is licensed under a Creative Commons Attribution 3.0 License .
个人分类: Time series|2222 次阅读|0 个评论
Introduction to Time Series Analysis-notes
xiaoxinghe 2013-4-4 10:03
个人分类: Time series|1 次阅读|0 个评论
[转载]R Tutorial Series (Repeated measures ANOVA)
ljxue 2013-3-20 23:53
http://rtutorialseries.blogspot.com/ Good teaching material. Another example for repeated measures ANOVA(This tutorial works for my case) http://ww2.coastal.edu/kingw/statistics/R-tutorials/repeated.html Two Way Mixed Factorial Designs Clean out your workspace, and then enter the data for this analysis bycopying and pasting this script into your R Console... ### begin copying with this line # create the data vectors for the four conditions pre.chicken=c(18,13,18,15,22,32,31,24,15) post.chicken=c(15,13,17,15,24,31,31,25,17) pre.pasta=c(17,30,18,13,23,27,27,24,23) post.pasta=c(19,31,18,13,24,27,26,28,26) # create the response variable vector SSS=c(pre.chicken,post.chicken,pre.pasta,post.pasta) # create the test condition labels test=rep(c(pre,post,pre,post),c(9,9,9,9)) # create the diet condition labels diet=rep(c(chicken,pasta),c(18,18)) # create the subject labels subj.chicken=rep(c(A,B,C,D,E,F,G,H,I),2) subj.pasta=rep(c(J,K,L,M,N,O,P,Q,R),2) # create the subject vector subject=c(subj.chicken,subj.pasta) # create the dataframe hill=data.frame(subject,diet,test,SSS) # clean up rm(pre.chicken,post.chicken,pre.pasta,post.pasta) rm(SSS,test,diet,subj.chicken,subj.pasta,subject) ### end copying with this line You should now have a data frame called hill in your workspace... ls() groceries groceries2 hill str(hill)'data.frame': 36 obs. of 4 variables: $ subject: Factor w/ 18 levels A,B,C,D,..: 1 2 3 4 5 6 7 8 9 1 ... $ diet : Factor w/ 2 levels chicken,pasta: 1 1 1 1 1 1 1 1 1 1 ... $ test : Factor w/ 2 levels post,pre: 2 2 2 2 2 2 2 2 2 1 ... $ SSS : num 18 13 18 15 22 32 31 24 15 15 ... These data were collected by Ben Hill (by now, Ben Hill, Ph.D.) as part of hissenior research project conducted in our department during the Fall 1999semester. His interest was in the role of brain serotonin in creating sensationseeking behavior. Since he couldn't manipulate brain serotonin directly (ourIRB would not permit it!), he chose to do so by way of diet, relying on thefinding that brain serotonin is elevated after a meal rich in carbohydrates.Therefore, he had 18 subjects come to the lab. All subjects were given theSensation Seeking Survey. Half the subjects were then given an evening mealconsisting primarily of chicken, while the other half were given a mealconsisting primarily of pasta. An hour later, the Sensation Seeking Survey wasreadministered. In the data frame, subject identifies the subject so thathis or her pre and post eating scores can be kept paired for the analysis,diet identifies the type of meal the subject was given, test contains thepre-post meal information, and SSS contains the survey scores. In this experiment, we have two explanatory variables, diet, which is abetween-subjects variable, and test, which is a within-subjects variable.Thus, in lingo familiar to social scientists, the design is called a 2 × 2 mixed factorial design with repeated measures on test.It's worth making sure you understand how the data frame is structured, so let'shave a look... hill subject diet test SSS 1 A chicken pre 18 2 B chicken pre 13 3 C chicken pre 18 4 D chicken pre 15 5 E chicken pre 22 6 F chicken pre 32 7 G chicken pre 31 8 H chicken pre 24 9 I chicken pre 15 10 A chicken post 15 11 B chicken post 13 12 C chicken post 17 13 D chicken post 15 14 E chicken post 24 15 F chicken post 31 16 G chicken post 31 17 H chicken post 25 18 I chicken post 17 19 J pasta pre 17 20 K pasta pre 30 21 L pasta pre 18 22 M pasta pre 13 23 N pasta pre 23 24 O pasta pre 27 25 P pasta pre 27 26 Q pasta pre 24 27 R pasta pre 23 28 J pasta post 19 29 K pasta post 31 30 L pasta post 18 31 M pasta post 13 32 N pasta post 24 33 O pasta post 27 34 P pasta post 26 35 Q pasta post 28 36 R pasta post 26 Note that all the SSS scores are in ONE column! The other columns completelyidentify the experimental conditions associated with that score, includingwhich subject it came from. By way of data summary... with(hill, tapply(SSS, list(diet,test), mean)) post pre chicken 20.88889 20.88889 pasta 23.55556 22.44444 Drat! There goes R arranging our factor levels in alphabetical order again,making our means table look backwards. Let's pretty that up... hill$test = factor(hill$test, levels=c(pre,post)) with(hill, tapply(SSS, list(diet,test), mean)) pre post chicken 20.88889 20.88889 pasta 22.44444 23.55556 Better! A nice graph might be in order as well... with(hill, boxplot(SSS ~ diet + test)) # output not shown with(hill, boxplot(SSS ~ test + diet)) # compare this one with the last one title(main=Ben Hill's SSS Data) title(ylab=SSS Scores) The SSS scores in the pasta group did go up as hypothesized, but there is a lotof within groups variability there, too. Will the effect turn out to bestatistically significant? Once again, the trick is in getting the model formula correct. In this case,we have two explanatory variables, and we want to see all possible main effectsand interactions. The test variable is within subjects... aov.out = aov(SSS ~ diet * test + Error(subject/test), data=hill) summary(aov.out) Error: subject Df Sum Sq Mean Sq F value Pr(F) diet 1 40.11 40.11 0.5094 0.4857 Residuals 16 1259.78 78.74 Error: subject:test Df Sum Sq Mean Sq F value Pr(F)test 1 2.7778 2.7778 2.1739 0.1598 diet:test 1 2.7778 2.7778 2.1739 0.1598 Residuals 16 20.4444 1.2778 The effect we're looking for would be shown by the diet × testinteraction. And sadly, it's not significant. Other Designs For reference, here are model formulae for a couple other common designs... Two factor design with repeated measures on both factors: DV ~ IV1 * IV2 + Error(subject/(IV1*IV2)) Three factor mixed design with repeated measures on IV2 and IV3: DV ~ IV1 * IV2 * IV3 + Error(subject/(IV2*IV3)) And so on.
2695 次阅读|0 个评论
暑假已结束了,总结下暑假自己看的书,感觉假期效率不高
tu312 2012-9-7 22:57
暑假已结束了,感觉假期总体效率不高,中间忙了些别的,还略微看了些心理学 总结下暑假自己看的专业书(不包括读物和论文等),其实很多以前略有接触,没有全部看。 Matlab Getting Started,Matlab User's Guide(这两个是自带的,全当总结用) Networks An Introduction M. E. J. Newman 2010 .pdf(这是复杂网络的入门) Mathematical.Statistics.and.Data.Analysis,.3ed,.Rice,.pdf(增补数理统计部分) Analysis of Financial Time Series 3rd Edition.Tsay 2010 .pdf(时间序列中级教材) Elementary Differential Equations.sixth edition C.Henry Edwards.pdf(增补指数、线性系统、边界值等) Differential equations, dynamical systems and an introduction to chaos.pdf(增补动力系统概念) Dynamical Systems(Jost).pdf(这个太难了,后来发现是数学专业的专题,看了一半不了了之) 现在正在看或马上准备看的 Nonlinear Systems - Analysis, Stability, and Control (Shankar Sastry).pdf Synchronization A universal concept in nonlinear sciences.Arkady Pikovsky, Michael Rosenblum and Jürgen Kurths.pdf Nonlinear Time Series Analysis.second edition,holger kantz and thomas schreiber.pdf 按照之前戴老师的书单,还有好多基础书要看啊! 哈哈,下次再总结下到目前为止数学基础看了多少
3086 次阅读|0 个评论
终于看完Analysis of Financial Time Series,暑假效率不高啊
tu312 2012-8-27 17:43
终于差不多看完Analysis of Financial Time Series,中间虽干了些别的,但总共大概花了2-3周才看完,暑假效率不高啊! 书的第4、5、9、12章没太看懂。 4 Nonlinear Models and Their Applications 很多东西没讲清楚,准备用下书好好增补,这个以后是重点 Nonlinear Time Series Analysis, Holger Kantz 5 High-Frequency Data Analysis and Market Microstructure直接在分析股票短线操作,没有金融相关基础 9 Principal Component Analysis and Factor Models 在分析个股的行业相关性等,最后的例子尽是分析必和必拓和淡水河谷的股票 12 Markov Chain Monte Carlo Methods with Applications 主要在介绍贝叶斯方法。本科课本只字未提贝叶斯学派,且比频域学派理解起来要困难。虽然之前暑假自学统计学时书上有专门介绍,但还是彻底看不懂,感觉区区60页很多东西没讲清楚。 接下来准备看看R语言,做做课后习题,作者的个人主页上还有不少补充材料,可以继续学习的。
5230 次阅读|0 个评论
昨天打印了时间序列分析,找了好久,还是这本不错
热度 1 tu312 2012-7-27 22:49
昨天打印了时间序列分析,找了好久,还是这本不错 Tsay 2010 Analysis of Financial Time Series 3rd Edition 汉米尔顿那本没找到清晰版的
3401 次阅读|2 个评论
物理化学史上的一颗明珠——霍夫梅斯特序列(Hofmeister Series)
热度 11 ChemiAndy 2012-7-11 05:55
复杂现象背后隐藏着简单的模式,简单的模式背后隐藏着基本的道理。 一棵苹果,掉在牛顿头上,就产生了万有引力,和现代力学; 正是因为牛顿发现并精准定义了这种模式:重物向“下”落,而不向上飞; 才导致这种模式背后规律,万有引力的发现。 科学发展史上也有很多这种“苹果”, 孟德尔看到了红花,白花,粉花的开花的统计规律,开创了遗传统计学,并导致了后来DNA的发现; 门捷列夫把元素和化学性质排成表格,发现了元素周期律; 路易斯发现了稳定化合物中元素成键的8电子配对律,并发展出了价键理论; 此外,把一些复杂的现象总结成为简单的模式或者概念,可以大大帮助我们理解一些规律, 比如,化学基团的亲电性和亲核性,物质的亲水性和疏水性。 所以,发现一种模式,就像发现了科学的矿井一样,可能挖掘出重大的理论或概念。 不过,还有很多模式或者现象还尚未被理解或解释, 比如,最近科学网上讨论的热水比冷水先结冰的现象,还有,这里要谈的物理化学发展史上的霍夫梅斯特序列。 100多年前,出生于捷克的科学家Hofmeister发现了一个与蛋白质变性剂有关的规律。 我们知道,煎鸡蛋时,蛋清会成为蛋白,就是因为煎锅热使蛋白质失去它的天然结构,转变成为了不透明的肽链聚合物。这种转变就称为蛋白质变性。此时蛋白质失去特有的结构和功能。不仅加热可以使蛋白质变性,加某些盐、糖、或者有机小分子比如尿素,也能使蛋白质变性,称为化学变性。你说通常往鸡蛋清里加食盐(NaCl)并没有看到蛋清变浑浊啊?是的,不同的盐有不同的变性效果。有的盐,加一点就可以使蛋白质变性,比如硫氰化钠(NaSCN),盐酸胍(GdmCl), 有的盐,则需要加很多才能起效,或者在达到最大溶解度时也不能使蛋白质变性,比如NaCl, Na2SO4。 我们也知道,盐溶解于水会成为离子,因此,加盐使蛋白变性的过程必然是离子起的作用,那么,把这些离子按照它们变性能力,或者说起变性作用时的浓度,按照大小排个序,这就是Hofmeister Series,霍夫梅斯特序列。 霍夫梅斯特发现的序列是这样的,SO 4 2- Cl - NO 3 - Br - I - ClO 4 - SCN - 从左往右使蛋白质变性的能力逐渐增加,事实上,左边的硫酸根能够稳定蛋白质的天然结构。 为什么只有阴离子呢?阳离子序列也是存在的,只不过,Hofmeister发现起变性作用的,主要是阴离子的功劳。 随后发现,Hofmeister发现的这个序列,对涉及离子的很多现象适用,比如,盐离子不仅影响蛋白质胶体的稳定性,而且影响其溶解度,即稀的盐溶液可以增加或减小蛋白质的溶解度。那么在同等浓度下,按照对蛋白质的溶解度大小的改变排列,可以发现相同的离子序列。 除了蛋白质溶液,离子对其它大分子胶体溶液的稳定性和溶解度,也有类似的序列; 除了胶体溶液,盐离子对纯的盐溶液的性质,也有相同序列。比如,加盐可以改变水的粘度和表面张力,对离子的这种能力列表,可以发现类似的Hofmeister序列。 图:霍夫梅斯特序列。注意序列左右两端对性质的改变能力正好相反。图片来源: Hofmeister Series 在过去的100年中发现的数十种序列中,虽然有小部分反例,但大多数序列中离子的位置是一致的。这说明在此序列背后,存在类似的规律决定了离子对液体水的性质的改变,和对蛋白质,多肽和DNA等对胶体溶液的性质的改变。当然,正如有的人反驳的那样,这些序列存在不能说明这些性质都是有相同的规律支配的。但是,至少可以肯定,在与离子有关的一些热力学和动力学规律中,离子某种性质起了主要或大部分作用。毕竟,静电作用(指离子-离子,离子-偶极)是离子溶液中所有分子间作用中最强的作用,其它作用包括溶剂水分子之间的偶极-偶极作用,所有种类之间的短程排斥,和色散、诱导作用。在水溶液中,后面这些作用相比静电作用要弱的多。 那么,有没有理论能解释这个某个现象的Hofmeister序列呢?还没有。比如,预测经典稀溶液活度系数的德拜-休克尔离子强度理论,和描述胶体稳定性的DLVO理论,均认为溶液性质只与离子的电荷和浓度有关,然而它们不能预测“同种电荷离子具有不同的Hofmeister效应”,这叫Ion specific effect,即离子特异效应。把离子的大小考虑进来,能够显著改进现有理论,这就是所谓的“电荷密度解释”。但是,只考虑“电荷密度”也不能完全解释Hofmeister序列,毕竟,水在其中的作用不可忽视。 目前,理论界关注的焦点是离子的溶剂化效应,即关注离子-水之间的作用。当前的一些现有理论,不管是离子强度理论,还是电荷密度理论,都把溶剂水看成连续的,均匀的,不变的。但是,我们早就知道,离子溶于水以后,会和水分子结合形成溶剂壳层(Hydration shell)。这种壳层结合会减少自由活动的水分子,或者减少可供大分子表面结合的溶剂分子数量。此外,离子在水中运动,会带着自己的溶剂壳层一起运动。当然,溶剂壳层中的水分子,并不是固定不变的,它们以一定的频率与外界的自由水分子进行交换。溶剂化效应至少从密度和扩散两个方面影响着整个液体水的性质,即含离子的水不再是均匀的,连续的。 阴离子和阳离子及其水合壳层示意图。注意水分子的取向,但图示水合数目 并不对应真实值 。 要想构造一个理论,来考虑溶剂的不均匀性,至少要搞明白离子对溶剂壳层的水分子有什么影响,对壳层之外的水分子有什么影响,这种影响能够持续多远。而这也正是目前争论的焦点。一种观点认为,离子对溶剂水的影响局限在壳层内,对壳层外的水分子没有任何影响,因此离子对蛋白质等胶体大分子稳定性的影响,通过与胶体分子直接接触起作用;这种观点称为“直接作用模型”;另外一种观点认为,离子不仅影响壳层内的水分子,而且影响壳层外的水分子,所以无需直接接触大分子,即可影响水中胶体大分子的溶解度或者稳定性。这种观点称为“间接作用模型”。支持直接作用模型的,主要是Bakker等发展的介电响应光谱发现壳层外的水分子的重取向运动(转动周期)与离子的存在没有明显关系。支持“间接作用模型”的实验主要是一些红外光谱,发现了水的氢键网络模型受到离子的影响,尽管这种影响的幅度有争议。 在这个领域,要想提出一个合理解释和一个理论模型,就要尽可能搜集所有实验事实,然后进一步设计实验验证。但是,在分子尺度上研究其壳层结构和动力学很难,因为水分子太小了,氢原子的量子效应也比较强;此外,要想解释已有的实验现象也很难,因为很多实验现象本身也很有争议。比如,绝大多数实验都是在阴阳离子共存的溶液中做的,在分解贡献时都难免采用含混不清的近似理论。最近几年,UC Berkeley的一帮人,包括Jia Zhou, Evan R. Williams等用质谱打出只包含一个离子的水分子簇并结合红外光谱(IRPD)进行研究,能够排除这个问题,但是红外光谱能够获取的信息还是很有限的。 按说,使用分子模拟方法应该很容易研究溶剂化效应,在实际中的确如此,比如用中子散射确定溶剂壳层中的水分子个数,一般要和模拟得到的结果做对比,因为实验本身的分辨率很低。不过,能够用来模拟水溶液的适用理论的准确度都不高:用经典力场吧,它们的参数都是拟合宏观实验值的,不保证微观结构的准确性;用密度泛函理论(DFT)吧,色散成很大问题,导致熔点、沸点跟实验值差100K以上,还不如经典力场。此外,所有分子动力学方法都基于经典运动方程,即牛顿运动方程,不能准确描述量子效应。(路径积分或质心分子动力学可以部分程度上模拟量子效应)。 这在描述水分子运动的时候尤其糟糕,比如,第一原理分子动力学模拟的水分子的扩散运动一般要比实验真实运动要慢~50%。 毫无疑问,Hofmeister series和ion specific effect背后,隐藏着离子-溶剂二元体系,和离子-溶剂-胶体大分子三元体系热力学的一些秘密。这些秘密能够帮助我们建立一个可预测性质的理论。然而,鉴于其中的物理和数学的复杂性,这个领域仍然在期待着天才的降临。 相关博文: 大气污染与硫酸根水合离子簇研究
个人分类: 科学进展|57406 次阅读|23 个评论
[转载]Pacific Asian Lecture Series: Sino-Capitalism-China's
zuojun 2012-5-26 04:39
UHawaii Manoa Campus Events Calendar Pacific Asian Lecture Series: Sino-Capitalism - China's Reemergence and more May 29, 4:15pm - 5:30pm Manoa Campus, Shidler College of Business, Faculty Lounge BusAd D-207 http://www.hawaii.edu/calendar/manoa/2012/05/29/18490.html More on Sino-Capitalism: http://www.eastwestcenter.org/news-center/east-west-wire/adapting-rise-sino-capitalism
个人分类: Uniquely Hawaii|1876 次阅读|0 个评论
Crowds
majian 2012-5-20 21:28
Bang Goes the Theory - Series 6 - Episode 4
个人分类: 百家|1 次阅读|0 个评论
[转载]泰勒级数和傅里叶级数
spirituallife 2012-5-9 16:09
还是写几笔把,不写这个问题就忘了。 但一定要老黄来合作,也就是老黄来当第一作者,俺排最后,他是我的活数学手册,俺说到哪,他就得给俺插入公式和插图。 1 泰勒级数 学微积分,有没有和我一样的,对泰勒级数的伟大震惊了? 如果没有,那你的微积分真是白学了。 泰勒级数为什么伟大?得从认知说起。 小时候,感觉计算器里面有鬼魂,不但能算加减乘除,连正弦余弦三角函数都能算,当时不知道怎么算这些东西,就认定计算器里面有鬼魂。 知的首要条件就是离散恶确定性,一个就是一个,两个就是两个,半个,其实是放大到小数点之后被认知的,至于无理数,也是一样,你的有个计算方法来认知,如果连个计算方法都没有,就是根本不可认知的。 泰勒级数就是提供了一个通用的计算方法,这个方法实在是太伟大了,啥东西都可以算,也就是把俺一直以为计算器里的鬼魂赶走了。 那么,泰勒级数到底干了些啥?怎么会有如此的威力。 没干啥,就是拿着一条直线,不断得去分割逼近,越来越接近你想要的结果。 其实,泰勒级数的灵魂,就是牛顿分割法,估计牛顿也是知道泰勒级数的形式的,只不过没有清晰地表达出来而已。 好了,深入一点谈泰勒级数。 我们的认知基础是离散的确定性,无论小数点后面多少位,这个数你必须是确定的,不能无理到,第N位是变化的,如果真是这样的数,真的没法认知。 这到底什么含义? 其本身就是把你需要认识的信息进行一个编码,这个编码,每一位可以代表一个维度信息,也就是说吧一个连续的数值,编码到一个离散的维度上来,这样我们才能够认知他。 更广泛的意义,已经不是数值了,没有大小的含义,纯符号的运算,只要把这个信息是可编码的,我们就能够在抽象空间内表达,根本不关心大小和顺序。 为什么可以不关心顺序? 就是因为编码到了空间维度上了,每一个维度是独立的,比如(x,y,z)你写成(y,x,z),也无妨,每一个空间维度是独立的,和顺序是无关的。 好了,我们现在知道,泰勒级数在干什么了,把一个有序的(连续)信息,编码到了一个独立的无序(即和序无关)维度离散空间上了,别的啥也没看。 为什么要做这样的变换? 刚才讲了,为了认知他,不做这个变换,是不可计算的,也就是不可认知的。 如何能够做到? 还是求助于几何原本。 几何原本给俺们提供了连个法宝,一个是直尺,一个是圆规。 先看直尺。 直尺到底直不直,其实无所谓,关键是直尺定义了一个东东——方向。 泰勒级数的本质就是在用方向信息,把一个曲线的变化,用无穷多个方向离散化,也就是原本是一个平面,我搞出无穷多条直线,每条直线代表一个方向,每个方向独立成一个维度,最后把这条曲线搞定。 综上所述,泰勒级数就是利用直尺,把连续(连续隐含有序)的函数曲线,变换到了离散的独立维度编码上来。 2 傅里叶级数 学微积分,第二个震惊,就是傅里叶级数。 当时,我对泰勒级数还没完全理解,离散数学是后来才深入领会的,对傅里叶级数的吃惊程度,和俺小时候对于计算器里有鬼魂一样。 为啥这么搞,那么搞,最后就分解成频率信息了呢?真是感觉是撞了狗屎运,才发现这么一个东西。 又来深入了,才发现也就是那么回事儿,不是狗屎运,也是必然。 前面说的,有关认知的都有效,就是一点,法宝变了。 泰勒用的是直尺,傅里叶用的是圆规,就这点差别。 这点差别还不得不细说,直尺提供的是个方向,圆规能够提供啥? 面积,你也可以说周长,其实园的周长是无法直接利用的,是经过面积等效出来的。 人的认知就这么一点,直尺提供了一个方向,无穷无尽,反正生命不息,冲锋不止,你只有往下去走。 圆规提供了一个原地打转,你也不知道转了多少圈,反正一直都这样转,唯一知道的是,这个面积是确定的。 傅里叶拿着圆规搞编码方案,这就有点烦,不想泰勒级数那么直观了,他在搞面积等效方案。 面积等效方案,产生了一个新东西,就是正交。也就是说面积不能重叠。 正交对于泰勒级数是不是存在? 其实一样存在,只不过泰勒级数用的法宝是直尺,直尺表示的是方向,根本不用管直尺到底直不直,方向这东西本来就是独立维度,不需要考虑正交,或者是天然的正交。 傅里叶级数就不一样,面积是有可能重叠的,一重叠,就不是独立维度信息了,因此特别强调正交。 正交无非是保证面积不重叠而已,大家都是独立的维度信息。 今天就到这里,后面老黄来补充公式和画图。 老黄在接着讲拉普拉斯,拉普拉斯是个大牛,总是被人忽视,很多搞数学的都喜欢吹捧高斯,俺怎么觉得拉普拉斯比高斯牛很多倍,拉普拉斯尽管人品卑鄙,但他的工作实在是数学的又一个让我吃惊的创举。 在后面才能讲离散编码的本质。
个人分类: Math|0 个评论
[转载]漫谈高数(一) 泰勒级数的物理意义
spirituallife 2012-5-9 16:09
2009-06-24 1:44 高等数学干吗要研究级数问题? -----------[转载请标明本文CU blog出处] 是为了把简单的问题弄复杂来表明自己的高深? No,是为了把各种简单的问题/复杂的问题,他们的求解过程用一种通用的方法来表示。 先提一个问题,99*99等于多少? 相信我们不会傻到列式子去算,口算也太难了而是会做一个迂回的方法,99*(100-1),这样更好算。那么995*998呢? 问题更复杂了,(1000-5)*(1000-2),式子比直接计算要复杂,但是口算却成为了可能。归纳一下,x*y这样的乘法运算或者幂次运算,如何直 接计算很麻烦的话,我们可以用因式分解的方法(中学生都能理解)来求解。 但是因式分解仍然不够通用,因为我们总是需要通过观察"特定"的待求解式子,找到一种规律,然后才能因式分解,这是我们从小学到中学数学方法的全部: 特定问题特定的解答方法。那么,到了高等数学,怎么办? 研究一种方之四海皆准的,通用的方法。 泰勒级数的物理意义是什么? 就是把方程g(x)=0的解,写成曲线方程的形式看看和x轴有什么交点。例如f(x)=x^2=5等价于g(x)=x^2-5=0和x轴的交点。而这个曲 线交点可以用直线切线的逼近方法(牛顿迭代法)来实现,这就是泰勒级数的物理意义: 点+一次切线+2次切线+...+N次切线。每次切线公式的常数,就是泰勒级数第N项的常数。OK,从泰勒级数的式子可以看到,为了保证两边相等,且取N 次导数以后仍然相等,常数系数需要除以n!,因为x^n取导数会产生n!的系数。泰勒级数,就是切线逼近法的非跌代的,展开式。 ------------------------------------------------------------------- 泰勒级数展开函数,能做什么?对于特定的x取值,可以求它附近的函数y=x^100展开以后可以求x=1附近的0.9999的100次方等于多少,计算过 程和结果不但更直观,而且可以通过舍弃一些高阶项的方法来避免不必要的精度计算,简化了计算,节省了计算时间(如果是计算机计算复杂数字的话)。在图像处 理的计算机软件中,经常要用到开方和幂次计算,而Quake III的源代码中就对于此类的计算做了优化,采用泰勒技术展开和保留基本项的办法,比纯粹的此类运算快了4倍以上。 还可以做什么呢? 对于曲线交点的问题,用方程求解的办法有时候找不到答案,方程太复杂解不出来,那么用泰勒级数的办法求这个交点,那么交点的精度要提高,相当于泰勒级数的 保留项要增加,而这个过程对应于牛顿--莱布尼茨的迭代过程,曲线交点的解在精度要求确定的情况下,有了被求出的可能。 看到了吧,泰勒技术用来求解高方程问题,是一种通用的方法,而不是像中学时代那样一种问题一种解决办法,高等数学之所以成为"高等",就是它足够抽象,抽象到外延无穷大。 那么,更感兴趣的一个问题是,对于高阶的微分方程表达的问题,怎么求解呢? 泰勒级数不行了,就要到傅立叶级数-傅立叶变换-拉普拉斯变化。这几个工具广泛用于各个领域的数学分析,从信号与系统到数理方程的求解。 中学数学和高等数学最大的区别是什么? 中学数学研究的是定解问题,例如根号4等于2。高等数学研究什么呢----它包含了不定解问题的求解,例如用一个有限小数位的实数来表示根号5的值。我们 用泰勒级数展开求出的根号5的近似值,无论保留多少位小数,它都严格不等于根号5,但是实际应用已经足够了。不可解的问题,用高等数学的通解办法,可以求 出一个有理数的近似解,它可以无限接近于上帝给出的那个无理数的定解。通解可行性的前提是,我们要证明这种接近的收敛性,所以我们会看到高等数学上册的课 本里面,不厌其烦的,一章接一章,一遍又一遍的讲,一个函数,在某个开区间上,满足某个条件,就能被证明收敛于某种求和式子。 具体的求解过程:先说说泰勒级数:一个方程,f(x)=0,求解x,它唯一对应x-f(x)二维图像上的一条曲线。那么x的求解过程可以用牛顿-莱布尼茨 逼近法求得(迭代)。例如x^2=5可以看成f(x)=x^2-5=0的求曲线和X轴的交点。牛顿迭代法可以用来求解线性方程的近似解。那么如何求解非线 性方程呢? f(x)用泰勒级数展开,取前N项(通常N=2),得到一个线性的方程,这个方程相当于是原来的曲线在求解点附近做了一条切线,其求解过程和牛顿迭代法等 价。迭代次数越多,越接近非线性。用泰勒级数来分解sin(t),把一个光滑的函数变成一些列有楞有角的波形的叠加。用傅立叶级数来分解方波,把有楞有角 的波形变成一些光滑曲线的集合。但是傅立叶级数舍弃项的时候,会产生高频的吉布斯毛刺。局部的收敛性不如泰勒级数展开----因为泰勒级数展开有率间的常 数因子。 举个例子,用泰勒级数求解欧拉公式。没有欧拉公式,就没有傅立叶变换,就没有拉普拉斯变化,就不能把高阶导数映射到e的倒数上面,也就无法把微分方程等价为一个限行方程(方程两端同除以e的x次导数。因为e的高阶x导数等于e的一阶导数)的两端,很明显: 将函数 , 和 写成泰勒级数形式: 将 代入可得: 欧拉公式有什么用? 它把实数的三角运算变成了复数的旋转运算,把指数运算变成了乘积运算,把纯微分方程的求解过程变成了指数方程的求解过程,大大简化了运算。
个人分类: Math|1 次阅读|0 个评论
Call for papers:Special Section on Nonlinear Time Series
热度 1 yangfanman 2012-5-3 11:52
2013_4EN.pdf Call for papers Special Section on Advances and Applications in Nonlinear Time Series Methods The Institute of Electronics, Information and Communication Engineers (IEICE) We are pleased to announce a Special Section (SS) of the IEICE’s new journal, “Nonlinear Theory and Its Applications, IEICE,” to be published in April 2013. The major part of this SS will focus on recent progress on both methodological advances in and novel applications of nonlinear time series methods. The topics of interest within the scope of this SS include, but are not limited to, the following areas: - Nonlinear time series methods for scalar time series: embedding, invariants and non-stationarity - Embedding and reconstruction - Multivariate recordings - causality and correlation - Novel network and recurrence based methods - Complex networks, complex systems and time series - Applications: climate, physiology and medicine, finance, physical processes Papers submitted to this SS will be peer-reviewed under the handling of the editorial committee of the SS. The deadline of the paper submission is July 10, 2012. Prospective authors are requested to carefully follow the submission process described below: (1) Submit a paper using the IEICE Web site ( https://review.ieice.org/regist_common_e.aspx?society=NOLTA ). Authors should choose " Nonlinear Time Series Methods" as a "Type of Issue (Section)/ Transactions" on the line screen. Please do not choose " ". (2) Send "Copyright Transfer and Article Charge Agreement" and "Confirmation Sheet of Manuscript Registration" by1. E-mail, FAX or postal mail to the following address: Tomomichi Nakamura Graduate School of Simulation Studies, University of Hyogo 7-1-28 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan E-mail: nolta.timeseries@gmail.com Fax: +81-78-303-1985 (please attach a cover sheet indicating the sender's name) The article charges until 30 pages: One of the authors is a member of IEICE 60,000 JPY Otherwise 65,000 JPY Please do not forget to send "Copyright Transfer and Article Charge Agreement" and "Confirmation Sheet of Manuscript Registration" by July 10, 2012. We cannot start the review process without them, even if we receive their manuscripts. For additional guidelines on manuscript preparation, please visit the following site: http://www.nolta.ieice.org/authors.html Please note that if accepted, authors are requested to pay for the article charges covering partial costs of publications, page charge cannot normally be waived. Both members and nonmembers of IEICE are invited to submit manuscript. However, we recommend that authors unaffiliated with IEICE apply for membership: http://www.ieice.org/eng/member/OM-appli.html Editorial Committee of the Special Section Guest Editors Michael Small (The University of Western Australia) Tomomichi Nakamura (University of Hyogo) Advisory Editor Yoshifumi Nishio (Tokushima University)
个人分类: 复杂网络|4206 次阅读|1 个评论
[转载]Time Series Econometrics
zhao1198 2012-1-28 12:32
Time Series Econometrics http://www.ect.uni-bonn.de/studium/wintersemester-10-11/time-series-econometrics Prof. Dr. Jörg Breitung Sommersemester 2010 Inhalt: Mit Hilfe der multivariaten Zeitreihenanalyse können dynamische Zusammenhänge zwischen makroökonomischen Zeitreihen beschrieben werden. Die Analyse der langfristigen Beziehungen zwischen den Zeitreihen kann mit Hilfe der Kointegrationsanalyse untersucht werden. Solche Kointegrationsbeziehungen zwischen trendbehafteten Zeitreihen werden häufig als ökonomische Gleichgewichtsbeziehungen interpretiert. Der Anpassungspfad zur langfristigen Gleichgewichtsbeziehung kann mit Hilfe eines Fehlerkorrekturmodells beschrieben werden. In der Veranstaltung sind praktische Übungen mit den Softwarepaketen Eviews und MulTi integriert. Univariate Analysis Description of time series Seasonal adjustment and trend filter ARMA-Models Nonstationary time series (ARIMA) Time varying variances (GARCH) Forecasting Multivariate Analysis VAR-Model Prediction and Causality Schätzung unter linearen Nebenbedingungen Lag order selection Structural (identified) VAR models Cointegration Spurious regression Asymptotic theory for nonstationary time series Two-step analysis of Engle-Granger Kointegrated VARs (Johansen’s ML analysis) Literatur Lütkepohl , H. (1991), Introduction to Multiple Time Series Analysis, Berlin: Springer Hamilton, J. (1994), Time Series Analysis, Princeton: Princeton University Press Lütkepohl , H. und M. Krätzig ( 2004 ), Applied Time Series Econometrics , Cambridge : Cambridge University Press.
个人分类: T_教学方法|1831 次阅读|0 个评论
Generalized non-linear strength theory
kongyuxia 2009-11-26 16:38
Title: Generalized Non-Linear Strength Theory and Transformed Stress Space Author: Yao, Y. P.; Lu, D. C.; Zhou, A. N. ;Zou, B Source: Science in china series e-engineering materials science, 2004, 47(6): 691-709 Abstract: Based on the test data of frictional materials and previous research achievements in this field, a generalized non-linear strength theory (GNST) is proposed. It describes non-linear strength properties on the Pi-plane and the meridian plane using a unified formula, and it includes almost all the present non-linear strength theories, which can be used in just one material. The shape of failure function of the GNST is a smooth curve between the SMP criterion and the Mises criterion on the Pi-plane, and an exponential curve on the meridian plane. Through the transformed stress space based on the GNST, the combination of the GNST and various constitutive models using p and q as stress parameters can be realized simply and rationally in three-dimensional stress state.
个人分类: 学术探索|3825 次阅读|0 个评论
“Nobel经济奖”与“时间序列分析”
zlyang 2009-11-2 21:54
最近跟风 Nobel Prize ,去 The Nobel Foundation 的官方网站 http://nobelprize.org 看了看,发现 Nobel 经济奖与时间序列分析有关系。 在 The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2003 里 写着: http://nobelprize.org/nobel_prizes/economics/laureates/2003/index.html for methods of analyzing economic time series with time-varying volatility (ARCH) Robert F. Engle III ( November 10, 1942 ) for methods of analyzing economic time series with common trends (cointegration) Clive W.J. Granger (September 4, 1934 May 27, 2009) 这两位得主都是研究 analyzing economic time series 的。所以采用复杂时间序列分析新方法进行经济学研究(属于经济计量学 econometrics ),是有可能获得诺贝尔经济学奖。 Robert F. Engle III 研究的是:自回归条件异方差 (autoregressive conditional heteroskedasticity) 。 Clive W.J. Granger 研究的是:共整合 (cointegration) 。 他还是组合预测( The combination of forecasts )方法的主要提出者之一。 参考文献 : Robert F. Engle, http://weber.ucsd.edu/~mbacci/engle/index.html Clive W.J. Granger, http://www.econ.ucsd.edu/~cgranger/ The combination of forecasts, with J. Bates, Operational Research Quarterly , 20, 1969, 451-468. http://dss.ucsd.edu/~cgranger/pubs.html 欢迎补充! 欢迎纠正本博文的任何错误! 相关链接: 《什么样的人品得到诺贝尔经济奖》 http://www.sciencenet.cn/m/user_content.aspx?id=265938
个人分类: 科研|3606 次阅读|0 个评论
时间序列表达数据分析工具
anny424 2009-9-11 18:30
参考文献: Microarray data analysis and mining approaches Francesca Cordero , Marco Botta and Raffaele A. Calogero Corresponding author: Raffaele A. Calogero, Department of Clinical and Biological Sciences, University of Torino, Italy. Briefings in Functional Genomics and Proteomics 2008 6(4):265-281; doi:10.1093/bfgp/elm034 Although two-sample differential expression analysis is probably the most common experiment, multi-series time-course microarray experiments are useful approaches for exploring biological processes. In these types of experiments, the researcher is frequently interested in studying gene expression changes over time and in evaluating trend differences between the various experimental groups . The large amount of data, multiplicity of experimental conditions and the dynamic nature of the experiments pose great challenges to data analysis. A comprehensive review of research in time series expression data analysis was published by Bar-Joseph in 2004 . Recently, maSigPro Conesa has published two methods for time-course microarray data analysis . One is maSigPro , and is part of Bioconductor packages. ...This will ultimately be used to find what are the profile differences between experimental groups. ANOVA-SCA The other is ANOVA-SCA and combines ANOVA-modeling and a dimension reduction technique to extract targeted signals from data bypassing structural noise. ANOVA-SCA basically applies PCA to the estimated parameters in each source of variation of an ANOVA model. ANOVASCA seems an effective approach for separating the data variability present in a complex time course experiment to extract the signal of interest from noisy data . fully Bayesian approach Angelini and coworkers have recently described a fully Bayesian approach to detect differentially expressed genes in time-course experiments. Their approach allows to explicitly use biological prior information and deals with various technical difficulties that arise in microarray timecourse experiments such as a small number of observations, non-uniform sampling intervals, missing or multiple data and temporal dependence between observations for each gene. Authors compared their method with that implemented in R-package time course and in the EDGE software claiming that their algorithm provides results which are much closer to a biologists choice and delivers a lower percentage of false positive and negative answers than other algorithms . Fischer and coworkers have compared methods for identifying differentially expressed genes on time-series microarray data simulated from artificial gene networks. They suggest the use of ANOVA variants of Cui and Churchill on the bases of simulated data and Efron and Tibshiranis empirical Bayes Wilcoxon rank sum test in the case experimental background cannot be effectively corrected. CHPM Shi has instead proposed an approach, based on a probabilistic continuous hidden process model ( CHPM ), to identify the various biological processes involved in a specific biological experiment. This method integrates time series expression data with GO biological processes , modelling the observed gene expression levels as being generated by a combination of multiple GO biological processes whose activity levels vary over time. OTHER TOOLs: STEM Short Time-series Expression Miner (STEM) (~8 time points or fewer). STEM allows researchers to identify significant temporal expression profiles and the genes associated with these profiles and to compare the behavior of these genes across multiple conditions. STEM is fully integrated with the Gene Ontology (GO) database supporting GO category gene enrichment analyses for sets of genes having the same temporal expression pattern. STEM also supports the ability to easily determine and visualize the behavior of genes belonging to a given GO category or user defined gene set, identifying which temporal expression profiles were enriched for these genes. DREM Dynamic Regulatory Events Miner (DREM) takes as input time series gene expression data and input that associates transcription factors with the genes they regulate . This regulatory information could come from Chromatin Immunoprecipitation (ChIP)-chip experiments or transcription factor binding site motif information. The transcription-factor gene regulation input does not need to be associated with specific time points. DREM after executing a computational method described in outputs an annotated dynamic regulatory map based on the data that can be interactively explored. The dynamic regulatory map highlights bifurcation events in the time series, that is places in the time series where sets of genes which previously had roughly similar expression level diverge. Often these bifurcation events can be explained by transcription factors selectively regulation a certain subset of genes. DREM annotates these events with transcription factors potentially responsible for them. DREM is related to another time series expression analysis software the Short Time-series Expression Miner ( STEM ) . While STEM focuses on identifying independent significant patterns in short time series data , DREM provides a global map of the gene regulation of the time series . The DREM method also incorporates in transcription factor-gene regulation information. DREM also is not limited to analyzing short time series data as STEM is. Some of the input file formats and options are the same in DREM as in STEM, in particular options related to gene filtering and the Gene Ontology analysis. For these aspects of DREM which are the same as in STEM, the relevant portions of the STEM manual have been incorporated into this manual. BiGGEsTS An integrated environment for the biclustering ( Madeira and Oliveira, 2004 ) analysis of time series gene expression data . Biclusters may be analyzed with Gene Ontology annotations to find out which contain statistically relevant biological information or even filtered or sorted according to several numerical and statistical criteria. 应用举例: STEM Comprehensive transcriptional profiling of NaCl-stressed Arabidopsis roots reveals novel classes of responsive genes Yuanqing Jiang and Michael K Deyholos* Address: Department of Biological Sciences, University of Alberta, Edmonton, Canada BMC Plant Biology 2006, 6:25 doi:10.1186/1471-2229-6-25 用STEM做了聚类,然后以GOTerm为层次标注各term中包含哪些cluster,有几个。 Combined analysis reveals a core set of cycling genes Yong Lu 1 , Shaun Mahony 2 , Panayiotis V Benos 2 , Roni Rosenfeld 3 , Itamar Simon 4 , Linda L Breeden 5 and Ziv Bar-Joseph 1 ,3 1 Department of Computer Science, Carnegie Mellon University, Forbes Avenue, Pittsburgh, Pennsylvania 15213, USA 2 Department of Computational Biology, University of Pittsburgh Medical School, Lothrop Street, Pittsburgh, Pennsylvania 15213, USA 3 Machine Learning Department, Carnegie Mellon University, Forbes Avenue, Pittsburgh, Pennsylvania 15213, USA 4 Department of Molecular Biology, Hebrew University Medical School, Jerusalem, Israel 91120 5 Basic Sciences Division, Fred Hutchinson Cancer Center, Fairview Avenue N, Seattle, Washington 98109, USA Genome Biology 2007, 8 : R146 doi:10.1186/gb-2007-8-7-r146 用STEM做了GO的显著性检验,P值,似乎大材小用 实战 STEM,总结如下: 1.用已经筛出来的差异基因做为输入,另外,用gene symbol来去除冗余(多个探针组对应同一蛋白,可以用UniRef);GO注释文件也以Gene symbol为ID(GO注释本来就是 注释 蛋白的,而非基因本身),但不可带有基因列表以外的Gene symbol。 2.可选STEM Cluster Method和K-means,设定Cluster数,进行GO Term富集分析。
个人分类: bioinformatics笔记|5106 次阅读|0 个评论

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