how to calcul Standard deviation of matrix

hello every one, i have a set of matrix and i wanna calculate a standard deviation of each matrix, here i tried :

std(M)

• it gives me a result in a vector, i wanna have only one result here also i tried :

std(M(:))

• an error appeared:

Error using var (line 65)
First argument must be single or double.

Error in std (line 38)
y = sqrt(var(varargin{:}));

Error in ndhif2 (line 178)

    s=std(M(:))

• i tried also:

std(double(M:))

• here the results all the same for all matrices= 0.5477
• i wonder how to correct it

Answer 1

[Walter Roberson]

std(M(:))

Answer 2

[Star Strider]

What is the result of calling whos just before you call std?

For example:

whos('M')
s = std(M(:))