Creating matrices with elements as a function of kroneckerDelta

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Jitendra Kumar Singh 2018-1-11

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https://ww2.mathworks.cn/matlabcentral/answers/376642-creating-matrices-with-elements-as-a-function-of-kroneckerdelta

评论： Jitendra Kumar Singh 2018-1-11

Hello everyone,

I want to create some spin matrices for which I know the elements as a function of matrix index and kroneckerDelta function. The functions are given here Spin Matrices.

Here's the snippet of the code:

S = 1;
syms m n
for m = -S:1:S
  for n = -S:1:S 
      sx{m,n} = (kroneckerDelta(m,n+1) + kroneckerDelta(m+1,n))*sqrt(S*(S+1) - m*n)/2;
      sy{m,n} = (kroneckerDelta(m,n+1) - kroneckerDelta(m+1,n))*sqrt(S*(S+1) - m*n)/(2*1i);
      sz{m,n} = kroneckerDelta(m,n)*m;
      s_plus{m,n} = kroneckerDelta(m,n+1)*sqrt(S*(S+1) - m*n);
      s_minus{m,n} = kroneckerDelta(m+1,n)*sqrt(S*(S+1) - m*n);
  end
end

The snippet gives errors in kroneckerDelta Function and the indices of the matrices. Can anyone help me in debugging this?

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Torsten 2018-1-11

编辑：Torsten 2018-1-11

在 MATLAB Online 中打开

By assigning values to m and n

for m = -S:1:S
  for n = -S:1:S

m and n become double.

Best wishes

Torsten.

Jitendra Kumar Singh 2018-1-11

在 MATLAB Online 中打开

Here is how I fixed the code. Thank you everyone for your comments.

 clearvars
S = 1;
for m = 1:1:(2*S+1)
    for n = 1:1:(2*S+1) 
        sx{m,n} = (double(eq(m, n+1)) + double(eq(m+1, n)))*sqrt(S*(S+1) - m*n)/2;
        sy{m,n} = (double(eq(m, n+1)) - double(eq(m+1, n)))*sqrt(S*(S+1) - m*n)/(2*1i);
        sz{m,n} = double(eq(m, n))*m;
        s_plus{m,n} = double(eq(m, n+1))*sqrt(S*(S+1) - m*n);
        s_minus{m,n} = double(eq(m+1, n))*sqrt(S*(S+1) - m*n);
    end
end