On Mon, 9 Nov 2009, J. wrote:
Hi everyone,
I created a four dimensional vector (dim (128,128,1,8)). This third
dimension is necessary for another function somewhere. Now I'd like to
perform a t-test on every vector of length 8 in my array on the fourth
dimension.
Vectorize the whole thing:
adf <- as.data.frame( aperm( A, c(4,1,2,3)))
tA2 <- array( mean(adf) / sd(adf) * sqrt(8), c(128,128,1))
HTH,
Chuck
I'd like to obtain a new array of three dimensions with dimensions 128x128x1
with all these test statistics.
I tried this with a double loop:
A <- array(rep(seq(-1:2),128*128*8),dim=c(128,128,1,8)) #in simulations I
fill the array with random variables
tA <- array(rep(NA,128*128),dim=c(128,128,1))
for (i in 1:128){
for (j in 1:128){
print(c(i,j))
tA[i,j,1] <- t.test(A[i,j,1,],alternative="two.sided",mu=0)$statistic
}}
This works, but it takes way to much time, since I'd like to run this about
500 times.
I read something about the apply function, but there I don't know how to
specify the outcome values ($statistic), plus I have some difficulties with
the specification of my vectors...
This doesn't work:
tA <- apply(smoothA,4,t.test$statistic)
"Error in t.test$statistic : object of type 'closure' is not subsettable"
I sought in the package multtest, but can't find any helpful function.
Thanks,
J.
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Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cbe...@tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
