Nested For Loops help

 Hello! 
I am attempting to use a nested for loop on two columns of data. Here's an example of what I am trying to accomplish
A = [1;2;3;4]
B = [4;3;2;1]
for i = 1:numel(A)
   for j = 1: numel(B)
       diff = A(i) - B(j)
   end
end

I want the output to be [(1-4) (2-4) (3-4) (4-4) (1-3) (2-3) (3-3) (4-3) etc] where it iterates through the A matrix completely but selects the same value from the B matrix each time. Essentially: A(1)-B(1), A(2)-B(1), A(3)-B(1), A(4)-B(1) and have an output matrix that contains all of the iteration outputs. So it should be a 16x1 matrix Any advice on what I am doing wrong?

[Stephen23]

DO NOT use diff as a variable name!

Because then the inbuilt (and very useful) function diff will not work!

Always check if a variable name is used:

which diff

Answer 1

[David Fletcher]

You're not retaining the variable 'diff' but just keep replacing it with the latest subtraction. You could initialize diff=[] before the loops and then change the assignment to diff=[diff A(i)-B(j)]. Computationally, it's not great, but it should do the job.

[Ife M]

Thank you so much!!

Answer 2

[Fahad HCT2021]

% Define variables
syms ;
f=@(i) ;

% Loop to create vector df1
for i= ;
   deriv=diff( );  % Find the general ith derivative of f
   df1(i)=subs( ); % Substitute x=1
end;  % DO NOT CHANGE CODE ON THIS LINE
df1  % Display the vector df1