[Rd] chi-square test

[Benjamin Chan [BRE]]

a warning message appears when i use the chisq.test ,but it doesnt
appear everytime, why?
"Warning message: 
Chi-squared approximation may be incorrect in:
chisq.test(matrix(c(20.1, 18.5, 2.6, 32.9, 23.5, 5.4), nc = 2)) "
 
why does the warning message appear, please?
Thank you very much
here is the data which I have tried appear and not appear warning
message
 
have warning message
(1.3,4.9,12.6,10.5,5.5,6.5,4.7,9.8,10.3,23.2,7.3,6.6)
(13.8,8.4,8.7,10.4,25.5,28.7,2.5,5.1)
(20.1,18.5,2.6,32.9,23.5,5.4)
 
doesnt have warning message
(32.7,8.6,2561.5,2726.5)
(44.4,17.4,2561.5,2726.5)
(44.4,17.4,32.7,8.6)
(13.9,22.3,5.1,17.4,32.3,12)
(8.1,5.2,13.8,11.5,2.6,15.8,15.5,9.6,6.7,14.2)
(13.9,17.4,22.3,1740,2230,1390)

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