integral of a matrix

I want to take the integral of an exponetial of a matrix but I got this error and dont know how fix it:

'Unable to perform assignment because the indices on the left side are not compatible with the size of

the right side.

Error in Untitled7 (line 12)

ggg(ss)=integral(fun,0,T,'ArrayValued',true);'

thanks in advance

clc
clear 
close all
M=ones(3,3);
Dmat=[1;2;3];
fun=@(t)expm(-M.*t)*Dmat;
T=1e-2;
g=integral(fun,0,T,'ArrayValued',true);

[Walter Roberson]

ss is not defined anywhere obvious, and you did a "clear" so we know it is not in the workspace. The code should error about ss not being defined.

[raha ahmadi]

Dear Walter Roberson

you are right. I did not know how can make this mistake (embarressed smiley face)

very sorry and very thanks for your attention

[Walter Roberson]

And when you do not have that (ss) in there, then no error message is emitted.

I notice your tags mention expm, which is the matrix exponential, but your code uses exp() which is element-by-element exponential.

[raha ahmadi]

two mistakes in 5 lines code! good for me !!

I m really sorry and thank you very much. I m very tired and ...I corrected it

I hope you best wishes

Answer 1

[Walter Roberson]

format long g
M = ones(3,3);
Dmat = [1;2;3];
fun = @(t)expm(-M.*t)*Dmat;
T = 1e-2;
g = integral(fun,0,T,'ArrayValued',true);
g

g = 3×1

0.00970297763432788 0.0197029776343279 0.0297029776343279

[raha ahmadi]

I appreciate your attention and hope you all best

Answer 2

[Scott MacKenzie]

You note:

I want to take the integral of an exponetial of a matrix

But,

exp(-M.*t)*Dmat;

is a vector, not a matrix. Try using the dot operator in your function definition:

exp(-M.*t).*Dmat;

[raha ahmadi]

Dear Scott MacKenzie

sorry you are right but in fact I need to calculate the integal of a multiplication of a exponensial of a matrix by a column vector "Dmat". Its a matrix multiplication not an element-wise multiplication.

Best regards