White, Charles E WRAIR-Wash DC wrote:
If you found my subject heading to be confusing then I'm sure you'll enjoy the example I've included below. I find the apply type functions to be wonderful for avoiding loops but when I use them with existing functions, I end up using loops anyway to extract the vectors I want. I would appreciate it if someone could show me how to avoid these loops. Thanks.
EXAMPLE: noise<-matrix(data = rnorm(15, mean=0, sd=1), nrow = 5, ncol = 3,
byrow = FALSE, dimnames = NULL)
measure<-apply(noise,2,t.test)
measure
tval<-NULL
df<-NULL
pval<-NULL
for (i in 1:length(measure)){
tval[i]<-measure[[i]][[1]]
df[i]<-measure[[i]][[2]]
pval[i]<-measure[[i]][[3]]}
data.frame(tval,df,pval)
Charles E. White, Biostatistician Walter Reed Army Institute of Research 503 Robert Grant Ave., Room 1w102 Silver Spring, MD 20910-1557 301 319-9781 WRAIR Home Page: http://wrair-www.army.mil/
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Charles,
Use a data.frame and sapply instead.
sapply(as.data.frame(noise), function(x) t.test(x)[1:3])
Sundar
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