how to solve array dimension for matrix multiplication issue?

Dear matlab expert, I have 2 variables which 1 has 366 x 1 and the other one has 348 x 1 matrix dimension, I want to multiply these 2 variables but I got an error because incompatible array sizes for this operation. how can I fix this?

[Walter Roberson]

What size of result do you want?

[Anak Agung Adhi Dermawan]

366 x 1

Answer 1

[Abderrahim. B]

Hi !

Yes, multiplication of two arrays with incompatible sizes will throw an error !

A possible solution is to pad (zero pad is the common method) the array that has smaller size.

Demo:

vec1 = randi(10, 366, 1) ;
vec2 = randi(10, 348, 1) ;

% zero padding
vec2 =[vec2 ; zeros((length(vec1) - length(vec2)), 1)] ;
size(vec1)

ans = 1×2

366 1

size(vec2)

ans = 1×2

366 1

% Multiplication
vec = vec1*transpose(vec2) ;
size(vec)

ans = 1×2

366 366

% Element wise multiplication
vec = vec1.*vec2 ;
size(vec)

ans = 1×2

366 1

There is an in-build function in MATLAB called pad that you can also use.

Hope this helps

[Anak Agung Adhi Dermawan]

it helps sir, but how can I change 0 value to other value?

[Abderrahim. B]

vec1 = randi(10, 366, 1) ;
vec2 = randi(10, 348, 1) ;

% zero padding
value = mean(vec2) ; % set value to whatever you want, I set it to the average of the vector.
vec2 =[vec2 ; value*ones((length(vec1) - length(vec2)), 1)] ;

% Multiplication
vec = vec1*transpose(vec2) ;
size(vec)

% Element wise multiplication
vec = vec1.*vec2 ;
size(vec)

[Anak Agung Adhi Dermawan]

thank you sir