How to obtain a vector (A) of 11 rows (output MATLAB Function block), from a vector (B) of 501 rows (input to the MATLAB Function block)?.

Size mismatch (size [1 x 1] ~= size [10 x 1]). The size to the left is the size of the left-hand side of the assignment. More information

% The following code corresponds to the MATALAB function block that gives an error in the Simulink model in which I am working:

function y=f(A,B)

y=sqrt((A).^2+(B).^2);

y=y(1:49:450,1)

For more information:

If I load the vectors (A y B) in workspace and run it in command windows the desired result is obtained. I need to extract vector elements in matlab function from Simulink. If this is not possible, how can I extract the elements of the vector at the output of the function without leaving Simulink?.

[Fangjun Jiang]

Resolve this error first.

A=ones(11,1);
B=ones(501,1);
y=sqrt((A).^2+(B).^2);

Arrays have incompatible sizes for this operation.

[Manuel Infante Francés]

Thank you for your answer Sr. Fangjun, although I may not have explained it well. The dimension of A is (501x1) and that of B is (501x1). I want to get the vector y of (11x1), where 11 are the elements of y chosen from 1 to 501 of 50 in 50 ([y1;y50;....;y500)] . The result of:

y=sqrt((A).^2+(B).^2); %Vector A y B están en workspace

executed in command windows is what I was looking for but when I try to implement it in Simulink inside MATLAB function block:

function y=f(A,B)

y=sqrt((A).^2+(B).^2);

y=y(1:49:450,1)

it gives the error: Size mismatch (size [1 x 1] ~= size [10 x 1]). The size to the left is the size of the left-hand side of the assignment, which prevents the simulation of the model from completing.

[Fangjun Jiang]

My confusion comes from the title of your question. I thought it indicated that A has 11 rows.

By the way, y(1:49:450) should have 10 elements, not 11.

size(1:49:450)

ans = 1×2

1 10

[Manuel Infante Francés]

Excuse me. Thank you.

Answer 1

[Fangjun Jiang]

The straight solution is to use below.

function y=f(A,B)
temp=sqrt((A).^2+(B).^2);
y=temp(1:49:450);

Simulink is strict on knowing the size of the variable and keep it fixed (although variable size is possible).

It's better to click "edit data" at the MATLAB Function block code editor and specify the size of input, output, parameters, temp variables, etc.

[Walter Roberson]

I predict that Simulink thinks that the output of the block is supposed to be a scalar. Either the size has been configured for the block or else the next block in the flow expects a scalar and the size is being back propagated.

[Fangjun Jiang]

I tried.

If the size of y is constrained through back progation, the error would be "Error in port widths".

If everything is default (-1 for inherited), the error for "y=y(1:49:450,1)" would be "Size mismatch (size [501 x 1] ~= size [10 x 1])"

If the size of y is specified as 1, or 10, the error for "y=y(1:49:450,1)" would still be "Size mismatch (size [501 x 1] ~= size [10 x 1])".

It makes sense because no matter what, y=sqrt((A).^2+(B).^2) determines the size of y to be 501x1.

So the OP's error message may not come from the exact code.

But anyway, the solution should sove the problem.

[Manuel Infante Francés]

I have followed your recommendation but the error persists.

An error occurred while running the simulation and the simulation was terminated

Caused by:

• Index exceeds array dimensions. Index value 50 exceeds valid range [1-1] for array 'temp'. Error in 'G_I_EKF_IMPUT_F_8/MATLAB Function8' (line 3) y=temp(1:49:450,1);

I have tested with A and b (inputs to the function) in a constant block in a separate model. The result is the desired. In the model I work with, the inputs come from two selectors (which in turn come from an Extended Kalman Filter block). Could the propagated error come. If so, how could I solve it?

[Fangjun Jiang]

This error is different. Put a break point at line y=temp(1:49:450,1) and debug it. You will see that most likely, the size of "temp" before this line is 1x1 or 1x500. You need to be certain of the size of the variable everywhere. Turn on signal size display in Simulink. Put the breakpoints in the MATLAB Function block code and run it line by line and observe the value of the variables.

[Manuel Infante Francés]

Thank you for your interest Mr. Walter I also think that the error could come along that line. I have tried and reviewed the settings of the MATALAB function, with inherited size, but it still gives errors in the dimensions.

[Manuel Infante Francés]

What do you mean by a breakpoint? Please, could you indicate the code? Thank you.

[Fangjun Jiang]

https://www.mathworks.com/help/matlab/matlab_prog/set-breakpoints.html

[Manuel Infante Francés]

Thank you.