MATLAB: How can i avoid the for loop in this case

for loop

a_matrix=zeros(10,4);
a=[3 6 7 8]';
for i=1:numel(a)
    a_matrix(a(i),i)=1;
end
disp(a_matrix)
     0     0     0     0
     0     0     0     0
     1     0     0     0
     0     0     0     0
     0     0     0     0
     0     1     0     0
     0     0     1     0
     0     0     0     1
     0     0     0     0
     0     0     0     0

Best Answer

Method one: logical equals:
>> a = [3,6,7,8];
>> V = 1:10;
>> M = double(V(:)==a) % requires MATLAB >= R2016b
M =
   0   0   0   0
   0   0   0   0
   1   0   0   0
   0   0   0   0
   0   0   0   0
   0   1   0   0
   0   0   1   0
   0   0   0   1
   0   0   0   0
   0   0   0   0
For earlier MATLAB versions replace == with bsxfun.
Method two: sub2ind:
>> M = zeros(10,4);
>> X = sub2ind(size(M),a,1:4);
>> M(X) = 1
M =
   0   0   0   0
   0   0   0   0
   1   0   0   0
   0   0   0   0
   0   0   0   0
   0   1   0   0
   0   0   1   0
   0   0   0   1
   0   0   0   0
   0   0   0   0
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