averaging successive points in matrix

I am new to matlab and I want to average a matrix M(26x149) in such away that 9 successive data points in the second dimension are averaged to have M(26,17) data. The division of 149/9 may not be exact but I want 16 data plus the remaining 5 points are also averaged to make the total data M(26,17).

here is the script I tried

a= 1:9:length(M)

 MM=mean(M(:,a))

but this doesn't solve my problem

Any help is highly appreciated.

Answer 1

[Andrei Bobrov]

M = randi(100,26,149);
n = 9;

[a,b] = size(M);
out = squeeze(nanmean(reshape([M,nan(a,mod(-b,n))],a,n,[]),2));

variant with use function blockproc from Image Processing Toolbox

out = blockproc(M,[size(M,1) n],@(x)mean(x.data,2));

[sisay]

Many thanks......