How to Compare Regression Slopes

How to Compare Regression Slopes

If you perform linear regression analysis, you might need to compare different regression lines to see if their constants and slope coefficients are different. Imagine there is an established r[……]

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Size Matters: Metabolic Rate and Longevity (Regression analysis sample)

Size Matters: Metabolic Rate and Longevity

John Tukey once said, “The best thing about being a statistician is that you get to play in everyone’s backyard.” I enthusiastically agree! I frequently enjoy reading and watching science-related material. This invariably raises questions, involving oth[……]

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数据分析之美:如何进行回归分析

1. 确定自变量与Y是否相关

证明:自变量X1,X2,….XP中至少存在一个自变量与因变量Y相关
For any given value of n(观测数据的数目) and p(自变量X的数目), any statistical software  package can be used to compute the p-value associated with the F-statistic using this distribution. Based on this p-value, we can determine whether or not to reject H0. (用[……]

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STAMP (Statistical Analysis of Metagenomic Profiles)

STAMP

StampIcon.png

Using STAMP to identify SEED subsystems which are differentially abundant between CandidatusAccumulibacter phosphatis sequences obtained from a pair of enhanced biological phosphorus removal (EBPR) sludge metagenomes(data originally described in Parks and Beiko, 2010).

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Meta分析(Meta-analysis)简介

Meta分析的由来: Meta分析(Meta-analysis)是心理学家Glass于1976年首次提出,原文是这样的: Meta-analysis refers to the analysis of analyses. I use it to refer to the statistical analysis of a large collection of results from individual studies for the purpose of integrating the findings. It connotes a rigorous alternative to t[……]

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真理在缩水,还是上帝在掷骰子?(转贴)

最近在Google Reader中看见科学松鼠会有两篇文章被频繁分享,名为《真理在缩水——现代科学研究方法并不尽善尽美?》()与(),下文简称《缩水》。文章很有意思,而实际上说的是我们的老本行——统计学,因此我在这里也发表一些我的想法和理解,包括这两年我在美帝学习的一些思考,部分内容受益于两位老师Kaiser和Nettleton教授,先向他们致谢(尽管他们永远都不会看到这篇文章)。同时我也要先说明一下,读这篇文章可能会很花时间(至少我花了大约二十小时写这篇文章),即使我的观点没有价值,我相信里面的引用文献是有价值的。 初读文章,我脑子里冒出的一句话是“上帝在跟我们掷骰子”,文中给出了[……]

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Using prcomp/princomp for PCA in R (三)

Testing i.pca ~ prcomp(), m.eigensystem ~ princomp()

1. Briefly about PCA 2. The modules/functions that implement PCA in GRASS & R 3. My claims (Entitled Comments) 4. Evidence (=the numbers derived from i.pca, prcomp, princomp, m.eigensystem using some MODIS surface reflectance bands).[……]

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Using prcomp/princomp for PCA in R (二)

############################### PCA ############################### install.packages(“vegan”) library(vegan) > STpcoa<-read.table(file=”bactera_16s_final.subsample.phylip.tre1.weighted.phylip.pcoa.axes”, header=T,row.names=1) > STpcoa axis1 axis2 axis3 axis4 Cellulose -0.020878[……]

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Using prcomp/princomp for PCA in R (一)

Difference between prcomp and princomp: ‘princomp’ can only be used with more units than variables” prcomp是基于SVD分解(svd()函数,princomp是基于特征向量eigen()函数) Good video source: http://www.youtube.com/watch?v=oZ2nfIPdvjY http://www.youtube.com/watch?v=I5GxNzKLIoU&feature=relmfu http://ww[……]

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4sample CA RDA analysis

  > gtsdata_test=read.table(“gtsdata.txt”, header=T) > gtsenv=read.table(“gtsenv.txt”, header=T) > gtsdata_data_t<-t(gtsdata_data) > decorana(gtsdata_data_t) Call: decorana(veg = gtsdata_data_t) Detrended correspondence analysis with 26 segments. Rescaling of axes w[……]

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