Problems in running for loop on keys on container maps

Hi all, I am very new to matlab and I have some problems in using container map. I have a ketSet with grid index 1,1 1,2 1,3 and I would like to run a for loop on that to do some dot product. My question is in the for loop p = 1:2, how can I cast the index into the numerical key of the map?

keySet = {'1,1', '1,2', '1,3'};
%use cell array
valueSet = {[2 3], [3 4], [9,6]};
M = containers.Map(keySet,valueSet);

for p=1:2
    dot(M('1,p'),M('1,p+1'))
end

Error using indexing
The specified key is not present in this container.

Answer 1

[Bruno Luong]

keySet = {'1,1', '1,2', '1,3'};
%use cell array
valueSet = {[2 3], [3 4], [9,6]};
M = containers.Map(keySet,valueSet);
for p=1:2
    dot(M(sprintf('1,%d',p)),M(sprintf('1,%d',p+1)))
end

ans = 18

ans = 51

[Tsz Tsun]

Thanks a lot ! : )