MATLAB Answers

Assigning values from one array to another if certain specifications are met.

1 view (last 30 days)
Tadas Grauzinis
Tadas Grauzinis on 13 Apr 2020
Edited: Adam Danz on 13 Apr 2020
I have a few arrays
A= 0 1 2 3 6 8 9 10
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
B= 20 5 15 10
9 8 2 1
C= 10 15
9 3
Bassically the first row of A contains special points from a line that goes from 0 to 10 and the other two rows are where the values from B( to second row) and C( to third row) should go. Second rows of B and C are corresponding points from the first row of A.
For example. Since B(2,1)=A(1,7) then B(1,1) should go to A(2,7) like this:
A= 0 1 2 3 6 8 9 10
0 0 0 0 0 0 20 0
0 0 0 0 0 0 0 0
The final result should look like this:
A= 0 1 2 3 6 8 9 10
0 10 15 0 0 5 20 0
0 0 0 15 0 0 10 0
I am very much still a beginner in Matlab. I am writing a script that would calculate shear forces and bending moments of a cantilever beam so any advice and/or suggestions would be greatly appreciated.

  0 Comments

Sign in to comment.

Accepted Answer

Adam Danz
Adam Danz on 13 Apr 2020
Inputs:
A= [ 0 1 2 3 6 8 9 10
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0];
B= [ 20 5 15 10
9 8 2 1];
C= [10 15
9 3];
Solution:
[isMatch, col] = ismember(B(2,:), A(1,:));
A(2,col(isMatch)) = B(1,isMatch);
[isMatch, col] = ismember(C(2,:), A(1,:));
A(3,col(isMatch)) = C(1,isMatch);
Result:
>> A
A =
0 1 2 3 6 8 9 10
0 10 15 0 0 5 20 0
0 0 0 15 0 0 10 0

  4 Comments

Show 1 older comment
Tadas Grauzinis
Tadas Grauzinis on 13 Apr 2020
What does isMatch do in A(2,col(isMatch))?
It seems to work with just col. I understand that if it would be just A(2,col) than it would be reffering to second row all col outputs(which are just what is needed), but what does (isMatch) add?
Adam Danz
Adam Danz on 13 Apr 2020
Good question. Suppose matrix B was
B= [ 20 5 15 10
9 8 200 1];
There is no match for 200 so col would return 0 for that match. A(2,col) would then return an error since indices must be positive, non-zero integers. So, col(isMatch) makes sure you're only selecting col values that correspond to matches. It's a safety net.

Sign in to comment.

More Answers (1)

Kevin Hellemans
Kevin Hellemans on 13 Apr 2020
Edited: Adam Danz on 13 Apr 2020
Hi,
I think this should do the trick:
A= [0 1 2 3 6 8 9 10; ...
0 0 0 0 0 0 0 0; ...
0 0 0 0 0 0 0 0];
B = [20 5 15 10; 9 8 2 1];
C=[10 15; 9 3];
A(2,B(2,:)) = B(1,:);
A(3,C(2,:)) = C(1,:);
disp(A)

  1 Comment

Tadas Grauzinis
Tadas Grauzinis on 13 Apr 2020
It reads the second rows of B and C as a position and places first row elements like this.
A=[ 0 1 2 3 6 8 9 10 0;
10 15 0 0 0 0 0 5 20;
0 0 15 0 0 0 0 0 10]

Sign in to comment.

Products


Release

R2020a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by