Matrices given to pt? [was: [R] for loops and counters]
There is a general rule that scalar operations (that is functions that work element-by-element and return a scalar result) preserve attributes including names, dims and dimnames. Similarly, there is a general rule about binary operations and attributes. These things should definitely be in the `R Language Definition', but that languishes as a draft. I am writing up comments on R internals (currently an appendix on `Writing R Extensions', and this will go there (the section on attributes is current work).
On Sat, 15 Jul 2006, Fran?ois Pinard wrote:
Hi, people. I was a bit intrigued by the message quoted below. Indeed, if pt() is given a matrix, it returns a matrix. Should this feature be documented? ?pt speaks about "a vector of quantiles", and says nothing about the type of what it returns. The same might presumably apply to other distribution-related functions. ----- Forwarded message from Martyn Plummer <plummer at iarc.fr> ----- From: Martyn Plummer <plummer at iarc.fr> Date: Thu Apr 10 10:07:01 2003 Subject: [R] for loops and counters Peter, You didn't say what goes wrong, but you mind find this version more useful tstat <- (matrix(means, k,k, byrow=TRUE) - matrix(means, k,k,byrow=FALSE))/rms pvalue <- 2*(1-pt(abs(tstat), df=df)) pvalue[upper.tri(pvalue)] S is designed to allow you to work with "whole objects", which means that for loops can (and should) be avoided. Martyn On 05-Oct-99 Peter B. Mandeville wrote:
I am trying to assign values to a vector (pvalue). Similar code works in C but not in R. What am I doing wrong?
r <- pvalue <- 0
for(i in (1:(k-1))){
for(j in (i+1):k){
r <- r+1
tstat <- (means[i]-means[j])/rms
pvalue[r] <- 2*(1-pt(abs(tstat),df))
}
}
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