mis match matrix dimension

Hi

Consider the example and propose a solution to the dimension mismatch.

Thank you very much

a = zeros(15,41);
b = ones(1,2);
for i = 1:length(a)
    a(:,i) = b;
end

Unable to perform assignment because the size of the left side is 15-by-1 and the size of the right side is 1-by-2.

[KSSV]

What you are trying to do?

[Life is Wonderful]

To copy the content of b into a,

[Dyuman Joshi]

In what manner do you want to copy the content of b into a?

[Life is Wonderful]

a has 15 rows and 41 columns, whereas b only has one row and two columns. The issue is that after the third iteration, the b matrix is surpassed.

• What are the alternatives if each row of b is duplicated to 15 rows of a ?
• How do I transfer b to a if index i is changing?
• How to transform a matrix 1 x 2 to a 15 x 41 ?

[Dyuman Joshi]

"The issue is that after the third iteration, the b matrix is surpassed."

Can you explain what do you mean this?

"How to transform a matrix 1 x 2 to a 15 x 41 ?"

Since the dimensions of b are not multiple of the dimensions of a, it is not possible to transform (or replicate in any manner) b into a. Though you can replicate to nearest dimension and crop the required size.

a = zeros(15,41);
b = [1 2];

What is the expected output for the above data?

[Life is Wonderful]

You can see how matrix dimension transformed from the article by @Bjorn Gustavsson

Answer 1

[Bjorn Gustavsson]

As the commenters have indicated your request is to non-specific to have one solution, while we all expect you to have one specific solution in mind. Therefore it is unlikely that the solutions we suggest will be the one you have in mind. You could do something like this:

a = zeros(15,41);
b = ones(1,2);
for i = 1:size(a,2) % It is better to use the size of a in the dimension you use it for, this makes the code robus and will work even in the case a is larger along the first dimension
  a(:,i) = b(1+rem(i,2)); % This will copy the elements in b into a i some order, probably not the one you have in mind, but perhaps?
end

You could also do something like:

a = zeros(15,41);
b = ones(1,2);
for i2 = 1:2:size(a,2), % another programming trick is to name the loop-variables to indicate their meaning, here i2 - since we're looping over the second dimension of a
    a(:,i2:(i2+1)) = repmat(b,size(a,1),1);
end

Since both elements of b are identical you could do something like this:

a(:) = b(1); % this will work for this specific case, but not when b(2) ~= b(1)

Your question indicate that you are very new to matlab-use. To get up to speed as efficiently and rapidly as possible I've come to understand that the on-ramp course/material is good - that is the Mathworks introduction to matlab and designed for this purpose.

HTH

[Life is Wonderful]

Perfect method to show how a question can be analysed; option 2 will solve the problem for me.

Thanks a lot for your help

Answer 2

[Nithin Kumar]

Hi,

I understand that you are trying to assign matrix "b" to matrix "a" where the order of matrices are not the same. You can apply assignment operation on matrices when they are of the same order.

Additionally, you can apply assignment operation on matrices if at least one of the two dimensions of both the matrices are equal using concatenation.

For more information on the matrix dimensions, kindly refer the following link Creating, Concatenating, and Expanding Matrices - MATLAB & Simulink - MathWorks India

I hope this answer resolves the issue you are encountering.

[Life is Wonderful]

I appreciate you helping me.

This is vague and doesn't support the dimension resolution when they're distinct.