I just added a new option nlines to plot.Predict to make it easy to get
interaction line plots for categorical predictors. To get the new
version type the following after running require(rms):
source('http://biostat.mc.vanderbilt.edu/tmp/plot.Predict.s')
Here are some examples:
require(rms)
n <- 100
set.seed(1)
gender <- c(rep('male', n), rep('female',n))
m <- sample(c('a','b'), 2*n, TRUE)
d <- datadist(gender, m); options(datadist='d')
anxiety <- runif(2*n) + .2*(gender=='female') + .4*(gender=='female' &
m=='b')
tapply(anxiety, llist(gender,m), mean)
f <- ols(anxiety ~ gender*m)
p <- Predict(f, gender=., m=.)
plot(p) # horizontal dot chart; usually preferred for categorical
predictors
Key(.5, .5)
plot(p, ~gender, groups='m', nlines=TRUE)
plot(p, ~m, groups='gender', nlines=TRUE)
plot(p, ~gender|m, nlines=TRUE)
Frank
Petar Milin wrote:
Sorry, I hope this will be the last (for now, at least).
Following your advices, I did:
n <- 100
anxiety <- c(rnorm(n, 10, 2.5), rnorm(n, 26, 3.2),
rnorm(100, 25, 3.1), rnorm(100, 10, 2.6))
m.status <- c(rep('married', n*2), rep('not married', n*2))
gender <- c(rep('male', n), rep('female', n),
rep('male', n), rep('female',n))
im <- as.integer(p2$m.status)
m.status <- as.factor(m.status)
gender <- as.factor(gender)
require(rms)
d <- datadist(gender, m.status); options(datadist='d')
ols1 <- ols(anxiety ~ m.status)
p1 <- Predict(ols1, m.status=.)
ols2 <- ols(anxiety ~ m.status * gender)
p2 <- Predict(ols2, m.status=., gender=.)
pdf('figs/anova.pdf', height=6, width=8)
par(mfrow=c(1,2), mar=c(4,4,1,1), cex=1.2)
with(p1, plot(1:2, yhat, type='l', xlab='marital status',
ylab='anxiety', ylim=c(5,30), lwd=1.2))
xyplot(yhat ~ im, groups=gender,
type='l', data=p2, ylim=c(5,30), xlab='marital status',
ylab='anxiety', scales=list(x=list(at=1:2,
labels=levels(p2$m.status))), col=c('black','black'),
lwd=1.2, label.curve=list(offset=unit(.3,"in")))
par(mfrow=c(1,1))
dev.off()
Graphs are great! However, now, they does not appear in one panel.
Sorry, again, for asking so many questions. I am trying to wrap this.
Best,
PM
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
