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{ Monthly Archives } November 2008

气泡图击败Data Snoop

转自：泡网
Data Snoop, 民科的神奇直线(google 始作俑者):

气泡图，数据击败Data Snoop:

R tip：
n=20;plot(rnorm(n),rnorm(n),cex=sqrt(abs(rnorm(n)))*10,pch=1,col=1:n);

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2008 11 27 lixiaoxu Chinese Comments (1)

“Confidence interval of R-square”, but, which one?

In linear regression, confidence interval (CI) of population DV is narrower than that of predicted DV. With the assumption of generalizability, CI of at is
,
while CI of is
.
The pivot methods of both are quite similar as following.
,
so .
,
so

of linear regression is the point estimate of

for fixed IV(s) model. [...]

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2008 11 24 lixiaoxu English Comments (1)

Wordpress (and WPMU) Plugin for R Web Interface

Download: RwebFriend.zip [Update] Including Chinese UTF8 Version

Plugin Name: RwebFriend

Plugin URL: http://lixiaoxu.lxxm.com/RwebFriend

Description: Set Rweb url options and transform [rcode]…[/rcode] or <rcode>…</rcode> tag-pair into TEXTAREA which supports direct submit to web interface of R. *Credit notes：codes of two relevant plugins are studied and imported. One of the plugins deals with auto html tags within TEXTAREA tag-pair, [...]

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2008 11 22 lixiaoxu English Comments (5)

Type III ANOVA in R

Type III ANOVA SS for factor A within interaction of factor B is defined as , wherein A:B  is the pure interaction effect orthogonal to main effects of A, B, and intercept. There are some details in R to get pure interaction dummy IV(s).
Data is from SAS example PROC GLM, Example 30.3: Unbalanced ANOVA for [...]

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2008 11 18 lixiaoxu English Comments (0)

DV predicted by two IVs, vs. triangular pyramid

– Diagram from Wiki
It is easier to imagine relation in three spatial vectors by their angles, than by their correlations. For standardized and s , , cosines of three angles of the triangular pyramid determinate the correlation matrix, thus, all statistics of the regressions and . Unexpected but imaginative results on [...]

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2008 11 14 lixiaoxu English Comments (1)