[R] multiple t-tests across similar variable names

[arun]

HI,
A typo in my solution:
row.names(res2)<-unlist(unique(lapply(strsplit(colnames(dat2),"_"),`[`,1)))

                                                                                 ^^^^
    
    

A.K.



----- Original Message -----
From: "Nundy, Shantanu" <snundy at chicagobooth.edu>
To: "r-help at r-project.org" <r-help at r-project.org>
Cc: 
Sent: Wednesday, October 10, 2012 7:09 PM
Subject: Re: [R] multiple t-tests across similar variable names

Hi everyone-

I have a dataset with multiple "pre" and "post" variables I want to compare. The variables are named "apple_pre" or "pre_banana" with the corresponding post variables named "apple_post" or "post_banana". The variables are in no particular order.

apple_pre orange_pre orange_post pre_banana apple_post post_banana
person_1
person_2
person_3
...
person_x


How do I:
1. Run a series of paired t-tests for the apple_pre variables and pre_banana variables? Would be great to do something like ttest(*.*pre*.*,*.*post*.*).
2. Print the results from these t-tests in a table with col 1=mean difference, col 2= 95% conf interval, col 3=p-value.

Thank you kindly,
-Shantanu

Shantanu Nundy, M.D.
University of Chicago

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