[R] Find if there is independence

[Ambrosini Alessandro]

Hello
I have the matrix

a<-matrix(c(2,1,0,1,2,2,1,5,7,2,5,12),nrow=6)
a

      [,1] [,2]
[1,]    2    1
[2,]    1    5
[3,]    0    7
[4,]    1    2
[5,]    2    5
[6,]    2   12

Suppose that in the first row we have 3 men of England, 2 with hair, and 1
no
In the second we have 6 italian men, 1 with hair and 5 no ...
I want to find if there is a dependence between men withouth hair and
nationality.
By the way, which is the simplest command to use to study the independence
in a matrix like the one that I wrote?
Using
> chisq.test(a)

        Pearson's Chi-squared test with Yates' continuity correction

data:  a
X-squared = 0, df = 1, p-value = 1

Warning message:
Chi-squared approximation may be incorrect in: chisq.test(a)

Why does it give me the warning message? What have to add into chisq.test(a)
?
And in which value I can understand the level of the dependence?
Thank you
Alessandro

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