How can I generate a matrix?

Hi, I have two array and I want to generate one matrix according to these arrays.

For example:

a={2,5,2,4,2,3,4,4,8}

b={1,3,1,3,4,2,3,3,2}

Matrix is 2 to 1 -> 1, 5 to 3 -> 1, 2 to 1 -> 2 (again) ...

Output:

Thanks for your helps.

Answer 1

[Simon]

Hi!

Loop over your a/b vectors and increase the specified matrix element:

M = zeros(max(a), max(b));

for n = 1:length(a)
  M(a(n), b(n)) = M(a(n), b(n)) + 1;
end

[net]

Thanks for your help.

Answer 2

[Laurent]

a={2,5,2,4,2,3,4,4,8};
b={1,3,1,3,4,2,3,3,2};
yourmat=zeros(8,5);
for ii=1:length(a)
   yourmat(a{ii},b{ii})=yourmat(a{ii},b{ii})+1;
end

Why are you using a cell array for a and b?

[net]

Array "a" is my states and "b" is my observations. I want to know that states and observations amount.

Sorry for my english.

[net]

Yes you are right, I wrote with wrong parenthesis. Thanks.

Answer 3

[Andrei Bobrov]

a=[2,5,2,4,2,3,4,4,8];
b=[1,3,1,3,4,2,3,3,2];

sz = [8 5];
out = nan(sz + 1);
out(2:end,2:end) = accumarray([a(:),b(:)],1,sz);
out(1,2:end) = 1:sz(2);
out(2:end,1) = 1:sz(1);

[Shani]

Andrei do you know about neural networks?

[net]

Thanks for your help.