[R] Are loops handled differently in newer versions of R?

[Michael Rennie]

Hi gang,

I'm perplexed- I have some code that uses for() loops that works fine in 
R version 2.8 on my mac, worked fine in version 2.8 on my old windows 
machine, but doesn't work in version 2.10 on windows.

The loop implements a function over a data frame (code is included below).

In Mac (running version 2.8), the results of the loop are what I expect:

 > p_unadj
[1] 0.034939481 0.015743706 0.089287030 0.001098538 0.039290594

But in Windows (running version 2.10.1), I get a bunch of NA's...

 > p_unadj
  A   B      C    D    E
NA NA NA NA NA

If I had to guess, I'd say that R v. 2.10 is handling the i in 
lab8.dat[,1] differently, given that it's keeping the row names in the 
output for p_unadj... but why would that stop it from applying the 
function?

Any thoughts or suggestions are welcome.

Cheers,

Mike

Here's the code...


#build the dataset

locn<-c("A", "B", "C", "D", "E")
n<-c(28, 14, 21, 52, 35)
corr.r<-c(0.40, 0.63, 0.38, 0.44, 0.35)

lab8.dat<-data.frame(locn, n, corr.r)
lab8.dat

attach(lab8.dat)

#write the function

calc.prob.t<-function(n, r)
#given a sample size (n) and correlation coefficient (r), returns the 
probability for that test
     {
     df<-n-2
     t<-(r-0)/(sqrt((1-r2)/df))
         probt<-2*(pt(t, df, lower.tail=FALSE))
     probt
     }

#try out the function...
calc.prob.t(lab8.dat$n[1], lab8.dat$corr.r[1])
#it works.

#write a loop to implement that function for every correlation in your 
dataset...


p_unadj<-numeric(length(lab8.dat[,1]))
p_unadj<-NULL
p_unadj

#all this just built an empty vector to store the results of our loop...

for ( i in lab8.dat[,1] )
         p_unadj[i]<-calc.prob.t(lab8.dat[i,2], lab8.dat[i,3])

p_unadj

#if executed on my Mac, running R v.2.8, this works (and did using 2.8 
on my old windows machine). Running v. 2.10 in Windows, I get NAs.

-- 
Michael D. Rennie, Ph.D.
Postdoctoral Fellow, Environmental and Life Sciences Program
Trent University
2140 East Bank Drive, DNA Building (2nd Floor)
Peterborough, Ontario K9J 7B8
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www.people.trentu.ca/michaelrennie