Why Does Matlab Say Matrix Must Be Square When Using mpower?

[MathewsMD]

When running the following code on Matlab:

>> y(i) = y(i-1) + (0.5 * y.^3 * exp(t^2 + t))*h

I get the error:

? Error using ==> mpower
Matrix must be square.

It seems fairly simple but I'm not quite sure what I'm overlooking. Any help with regards to what I may be doing wrong would be greatly appreciated!

 

[MathewsMD]

I've gotten to:

>> y(i) = y(i-1) + (0.5 * y.^3 * exp(t.^2 + t))*h
? Error using ==> mtimes
Inner matrix dimensions must agree.

But the code still seems to be invalid.

 

[FactChecker]

Isn't y.^3 * exp(t.^2 + t) trying to multiply two row vectors y.^3 times exp(t.^2 + t)? You need to transpose one of them or do element wise multiplication.
P.S. To debug equations, try small part calculations and see which ones abort. Also, the size function helps you see what the dimensions are.

 

[kreil]

Use .^ and .* instead of ^ and *. The former perform elementwise operations, which is what you want here I believe.

* works fine if at least one operand is a scalar. But if you have two vectors, or a mixture of vectors and matrices, then they need to have compatible dimensions to use * (common inner dimension, i.e. NxM * MxP)

 

[alphy]

Hello,

Thank you for reaching out for help with your error code in Matlab. I understand that you are trying to run the code:

y(i) = y(i-1) + (0.5 * y.^3 * exp(t^2 + t))*h

and you are receiving the error message:

? Error using ==> mpower
Matrix must be square.

Based on the error message, it seems that the issue may be with the dimensions of the matrix or vector that you are using in your code. The mpower function in Matlab is used for matrix exponentiation, which requires the matrix to be square (equal number of rows and columns).

In your code, you are using the variable "y" in the expression "y.^3", which suggests that "y" may be a vector rather than a square matrix. This may be causing the error. I would suggest checking the dimensions of "y" and making sure it is a square matrix before using the mpower function.

Additionally, it may be helpful to check the dimensions of all the variables used in the expression and make sure they are compatible with each other. This could also help identify the source of the error.

I hope this helps. If you continue to have trouble, please provide more information about your code and the values of the variables used so that I can further assist you. Good luck!