Daniel Malter wrote:
put another condition in your loop
if(all.equal(x,y)=TRUE) i=i+1 else t.test...
something in that direction.
Sorry, but that's neither valid R code nor sensible in this case.
See my suggestions below.
best,
daniel
-------------------------
cuncta stricte discussurus
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Auftrag von Amit Patel
Gesendet: Thursday, July 09, 2009 9:20 AM
An: r-help@r-project.org
Betreff: [R] T.test error help
Hi I am implementing the t.test in a loop and where the data is the same i
get an error message.
Error in t.test.default(Samp3, Samp1, na.rm = TRUE, var.equal = FALSE, :
data are essentially constant
The script i am using is
for (i in 1:length(zz[,1])) {
for(i in seq_along(zz[,1])){
should be safer.
Samp1 <- zz[i,2:17]
Samp2 <- zz[i,18:33]
Samp3 <- zz[i,34:47]
Samp4 <- zz[i,48:63]
TTestResult[i,2] <- t.test(Samp2, Samp1, na.rm=TRUE, var.equal = FALSE,
paired=FALSE, conf.level=0.95)$p.value
TTestResult[i,3] <- t.test(Samp3, Samp1, na.rm=TRUE, var.equal = FALSE,
paired=FALSE, conf.level=0.95)$p.value
TTestResult[i,4] <- t.test(Samp4, Samp1, na.rm=TRUE, var.equal = FALSE,
paired=FALSE, conf.level=0.95)$p.value
}
Is there a way to make my loop ignore this problem and go onto the next
iteration
yes, you can wrap it in try() and check the object with
if(inherits(object, "try-error")) later on in order to do something
different (e.g. assign an NA) in case of an error.
Uwe Ligges
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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.