integral of a matrix

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raha ahmadi
raha ahmadi 2021-6-19
评论： raha ahmadi 2021-6-19
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);
  4 个评论
显示 2更早的评论
Walter Roberson
Walter Roberson 2021-6-19
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
raha ahmadi 2021-6-19
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

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采纳的回答

Walter Roberson
Walter Roberson 2021-6-19
Ran in:
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

更多回答（1 个）

Scott MacKenzie
Scott MacKenzie 2021-6-19
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;
  1 个评论
raha ahmadi
raha ahmadi 2021-6-19
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

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