R help - Jan 2008 - In chisq.test(x) : Chi-squared approximation may be incorrect

Hello,

 

I received the following warning when running chi-square;

n  Is there a way to catch the 'error' code of 'warning' after
run
chisq.test(x)?

n  What does this error mean?

 

Thank you for your help.

 

 


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Hi!
 the warning you got
"Chi-squared approximation may be incorrect"
is because probably there are less than 5 observations in
the cell. Maybe will help to 
try fisher.test()

Cheers

Anna







----- Messaggio originale -----
Da: My Coyne <mcoyne@boninc.com>
A: r-help@stat.math.ethz.ch
Inviato: Lunedì 14 gennaio 2008, 21:51:30
Oggetto: [R] In chisq.test(x) : Chi-squared approximation may be incorrect

Hello,

 

I received the following warning when running chi-square;

n  Is there a way to catch the 'error' code of 'warning' after
run
chisq.test(x)?

n  What does this error mean?

 

Thank you for your help.

 

 


    [[alternative HTML version deleted]]

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"My Coyne" <mcoyne at boninc.com> wrote in
news:000e01c8573a$ad60c8a0$082259e0$@com: 
> I received the following warning when running chi-square;
> 
> n  Is there a way to catch the 'error' code of 'warning'
after run
> chisq.test(x)?
It is not an error message. It is a warning message. When I assign the 
result of chisq.test(.) to an object and then look at its structure 
with str(), I do not see the warning message "in there". Instead the 
message appears on the console. When you look at the chisq.test 
function itself you see that any "E" less than 5 will trigger the 
warning:

if (any(E < 5) && is.finite(PARAMETER)) 
        warning("Chi-squared approximation may be incorrect")

You should be able to check the <object>$expected matrix in a similar 
manner if you goal is to process a large number of tables 
programatically. 
> 
> n  What does this error mean?
See above. Consider invoking chisq.test with the simulate.p.value 
option.

-- 
David Winsemius