Element by element multiplication of a matrix

I have a function f = e^(tH), where H is a square matrix. I want to compute this function for each value of t = 0:10:100 so I can plot f against t. Using .* is giving an error (sizes not compatible). What can I do?

Answer 1

[Paul]

For the matrix exponential:

% example data
H = [1 2;3 4];
t = 0:5;
f = cell2mat(cellfun(@expm,mat2cell(H.*reshape(t,1,1,[]),2,2,ones(1,6)),'UniformOutput',false));
% compare a few cases by hand
f(:,:,2) - expm(H*t(2))

ans = 2×2

0 0 0 0

f(:,:,end) - expm(H*t(end))

ans = 2×2

0 0 0 0

If f is supposed to be element-by-element exponential:

f = exp(H.*reshape(t,1,1,[]))

f = 
f(:,:,1) =

     1     1
     1     1


f(:,:,2) =

    2.7183    7.3891
   20.0855   54.5982


f(:,:,3) =

   1.0e+03 *

    0.0074    0.0546
    0.4034    2.9810


f(:,:,4) =

   1.0e+05 *

    0.0002    0.0040
    0.0810    1.6275


f(:,:,5) =

   1.0e+06 *

    0.0001    0.0030
    0.1628    8.8861


f(:,:,6) =

   1.0e+08 *

    0.0000    0.0002
    0.0327    4.8517

Answer 2

[Star Strider]

I have absolutely no idea what result you want.

Try this —

H = [1 2; 3 4]*0.01;
t = 0:10:100;

for k = 1:numel(t)
    f{k} = exp(t(k)*H);
end

figure
hold on
for k = 1:numel(t)
    plot(t(k)*[1 1; 1 1], f{k}, '.-')
end
hold off
grid

Also, consider the expm function, since ‘element-by-element’ is not precisely clear in this context.

.