Problem with skewness command

I'm following the example for skewness, but get an error message:

>> X = randn([5 4])

X =

0.5377 -1.3077 -1.3499 -0.2050

1.8339 -0.4336 3.0349 -0.1241

-2.2588 0.3426 0.7254 1.4897

0.8622 3.5784 -0.0631 1.4090

0.3188 2.7694 0.7147 1.4172

>> y = skewness(X)

Error using nanmean

Too many input arguments.

Error in skewness (line 39)

x0 = x - repmat(nanmean(x,dim), tile);

Best regards,

Tommy