R help - Feb 2008 - How to make t.test handle "NA" and "essentially constant values" ?

Hi,

First problem:
> test <- matrix(c(1,1,2,1), 2,2)
> apply(test, 1, function(x) { t.test(x) $p.value })
Error in t.test.default(x) : data are essentially constant

Second problem:
> test <- matrix(c(1,0,NA,1), 2,2)
> apply(test, 1, function(x) { t.test(x) $p.value })
Error in t.test.default(x) : not enough 'x' observations

How to make t-test ignores this errors ?

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Hi

r-help-bounces at r-project.org napsal dne 12.02.2008 09:09:23:
> Hi,
> 
> First problem:
> > test <- matrix(c(1,1,2,1), 2,2)
> > apply(test, 1, function(x) { t.test(x) $p.value })
> Error in t.test.default(x) : data are essentially constant
make your data not constant
> 
> Second problem:
> > test <- matrix(c(1,0,NA,1), 2,2)
> > apply(test, 1, function(x) { t.test(x) $p.value })
> Error in t.test.default(x) : not enough 'x' observations
increase number of observations

> 
> How to make t-test ignores this errors ?
Well, the procedure is complaining that you do not give it correct data. 
You shall be gratefull for a great software which prevent you from making 
silly things as try to compute t.test when data have zero variantion or 
number of observations is 1.

Regards
Petr
> 
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> 
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