cant mutplaye matrix by vector
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heloo i have this code
clc;
clear all;
R=5;
C=100e-6;
L=10e-3;
U=5;
A=[0 1/C;-1/L -R/L];
x=[0;0];
t=linspace(0,0.5,4);
t_delta=t(2)-t(1);
x_0=[0;0];
for i=1:length(t)
x(:,i+1)=t(i)*A
end
i have this code and i want to multipay A by t,but i get this eror: Assignment has more non-singleton rhs dimensions than non-singleton subscripts
how do i fix it ?
2 个评论
Guillaume
2018-1-4
how do i fix it ?
We don't know since we have no idea what you're trying to do.
t(i)*A results in a 2x2 matrix that you're trying to put in a 2x1 section of a matrix. That's never going to work.
In addition, as commented in your previous question, growing the x matrix is a bad idea. In this particular case, it's not even clear that the loop is needed.
回答（2 个）
Jan
2018-1-4
Your A is 2x2 matrix and x is a 2x1 vector. Then:
x(:,i+1)=t(i)*A
has a 2x2 matrix on the right and a 2x1 vector on the left side.
It is not clear what you want to calculate. Start with writing it down with pencil and paper. Then create a clear an meaningful comment in the code, which explains, what you want to achieve. Afterwards writing the code (or suggesting an improvement) is much easier.
4 个评论
tomer polsky
2018-1-4
Please take the time to
- proofread your posts
- understand the comments you're given and answer them clearly
The code you posted multiply t(i) by A. Then, you state you want to multiply x(i). Which is it?
You've been told by two different persons that the result for each step is 2x2 matrix, which you can't stuff into a 2x1 vector. Until we know what you want to do with these 2x2 matrices, we can't help you.
edit: could have done with proofreading my own post!
tomer polsky
2018-1-4
Jan
2018-1-4
t(i) is a scalar, A is a 2x2 matrix. Multiplying them creates a 2x2 matrix. If you state, that you want to get a 2x1 vector, a multiplication is not the right operation.
Star Strider
2018-1-4
If you are doing a state-space simulation, you are doing it incorrectly. You need to use a matrix exponential (the expm function), with the correct matrix multiplications.
See if this does what you want:
for i=1:length(t)
x(:,i) = expm(t(i)*A) * [1; 1] + x_0
end
You need to include the ‘A’, ‘B’, and ‘C’ matrices. (I created ‘B’ as [1;1] to produce a column vector output for ‘x’. Use your own matrices in the calculation.)
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2018-1-4
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