On Wed, 28 Jan 2009, Michael Pearmain wrote:
Hi All,
I've been having a little trouble with creating a loop that will run a a
series of t.tests for inspection,
Below is the code i've tried, and some checks i've looked at.
I've used the get(paste()) idea as i was told previously that the use of the
eval should try and be avoided.
I've run a single syntax to check that my systax is correct and works
without any problems
t.test(channel.data.train$News~channel.data.train$power)
Can anyone offer any advice?
There's the additional problem that if your code worked it would do 16 t-tests
but only report the last one.
Assuming you want them printed
for(v in names(channel.data.train)[1:16]) {
print(v)
print(t.test(channel.data.train[[v]]~channel.data.train$power)
}
or
for(v in names(channel.data.train)[1:16]){
test <- eval(bquote(.(v)~power, data=channel.data.train)
print(eval(test))
}
This sort of use of eval is fairly harmless.
-thomas
Many thanks
Mike
str(channel.data.train$power)
num [1:9913] 0 0 0 0 0 0 0 0 0 0 ...
summary(channel.data.train$power)
Min. 1st Qu. Median Mean 3rd Qu. Max.
0.0000 0.0000 0.0000 0.2368 0.0000 1.0000
names(channel.data.train)
[1] "News" "Entertainment" "Communicate"
[4] "Lifestyle" "Games" "Music"
[7] "Money" "Celebrity" "Shopping"
[10] "Sport" "Film" "Travel"
[13] "Cars" "Property" "Chat"
[16] "Bet.Play.Win" "config" "exposed"
[19] "site" "referrer" "started"
[22] "last_viewed" "num_views" "secs_since_viewed"
[25] "register" "secs.na" "power"
[28] "tt"
for(i in names(channel.data.train[,c(1:16)])){
+
t.test(get(paste("channel.data.train$",i,"~channel.data.train$power",sep="")))
+ }
Error in get(paste("channel.data.train$", i, "~channel.data.train$power",
:
variable "channel.data.train$News~channel.data.train$power" was not found
--
Michael Pearmain
Senior Analytics Research Specialist
Google UK Ltd
Belgrave House
76 Buckingham Palace Road
London SW1W 9TQ
United Kingdom
t +44 (0) 2032191684
mpearm...@google.com
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Thomas Lumley Assoc. Professor, Biostatistics
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