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t.test() on a list

5 messages · Bert Gunter, PIKAL Petr, Gang Chen

Original
Gang Chen
# 
I have a list, myList, with each of its 9 components being a 15X15
matrix. I want to run a t-test across the list for each component in
the matrix. For example, the first t-test is on myList[[1]][1, 1],
myList[[2]][1, 1], ..., myList[[9]][1, 1]; and there are totally 15X15
t-tests. How can I run these t-tests in a simple way?

TIA,
Gang
Bert Gunter
# 
I am sure you will get helpful answers. I am almost as sure that you
shouldn't be doing this. I suggest you consult with your local statistician.

-- Bert Gunter 

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Gang Chen
Sent: Thursday, October 02, 2008 11:24 AM
To: r-help at stat.math.ethz.ch
Subject: [R] t.test() on a list

I have a list, myList, with each of its 9 components being a 15X15
matrix. I want to run a t-test across the list for each component in
the matrix. For example, the first t-test is on myList[[1]][1, 1],
myList[[2]][1, 1], ..., myList[[9]][1, 1]; and there are totally 15X15
t-tests. How can I run these t-tests in a simple way?

TIA,
Gang

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Gang Chen
# 
I appreciate your suggestion. The example I provided was fabricated
because I was only focusing on the programming perspective on how to
deal with such a data structure, not real statistical issues. Do you
mind elaborating a little more why that would not be appreciate? I
know I can do it with a couple of loops,  but I still appreciate
suggestions on how to write a line or two to run t-tests on such a
data structure.

Thanks,
Gang
On Thu, Oct 2, 2008 at 5:11 PM, Bert Gunter <gunter.berton at gene.com> wrote:
3 days later
PIKAL Petr
# 
Hi

maybe not an answer you like but

apply(do.call(rbind, lapply(myList, c)), 2, t.test)

shall give you desired results

Regards
Petr


r-help-bounces at r-project.org napsal dne 02.10.2008 23:25:23:
wrote:
statistician.
mailto:r-help-bounces at r-project.org] On
http://www.R-project.org/posting-guide.html
1 day later
Gang Chen
# 
Thanks a lot, Petr! This works perfect!

myList was actually a list of data.frame, and the command line
initially choked. But once I converted it to matrix, it worked like a
charm:

apply(do.call(rbind, lapply(lapply(myList, as.matrix), c)), 2, t.test)

Thanks,
Gang
On Mon, Oct 6, 2008 at 9:42 AM, Petr PIKAL <petr.pikal at precheza.cz> wrote: