MATLAB Answers

Calculating the sum of each row in a matrix.

25 views (last 30 days)
Serra Aksoy
Serra Aksoy on 7 Feb 2020
Edited: Guillaume on 12 Feb 2020
Hi,
I have a code like this:
X = [1 2 3 4 5;
3 5 7 9 11;
2 4 6 8 10;
3 9 12 15 18];
minx = min(X, [ ], 2); %min of each vector
maxx = max(X, [ ], 2); %max of each vector
result = X >= reshape(minx, 1, 1, [ ]) & X <= reshape(maxx, 1, 1, [])
When i run it,
result is 4x5x4 logical and
val(:,:,1) =
1 1 1 1 1
1 1 0 0 0
1 1 0 0 0
1 0 0 0 0
Here i have a question.
I would like to see the sum of each row with names.
In val(:,:,1), the sum of first row= A11, sum of second row= A12, sum of third row= A13 and sum of fourth row=A14 .
Likewise for
val(:,:,2) =
0 0 1 1 1
1 1 1 1 1
0 1 1 1 1
1 1 0 0 0
sum of first row= A21, sum of second row= A22,...
I tried to do this with creating a 4X4 matrix A which consist of the sum values A11, A12, A13 A14, .... But i cant do it.
Any help is appreciated.

  3 Comments

Stephen Cobeldick
Stephen Cobeldick on 7 Feb 2020
"I would like to see the sum of each row with names."
Putting numbers into variable names is a sign that you are doing something wrong.
Putting meta-data into variable names is a sign that you are doing something wrong.
Accessing variable names dynamically is one way that beginners force themselves into writing slow, complex, obfuscated, buggy code that is hard to debug. Read this to know why:
You can trivially access the elements of an array using indexing. Indexing is neat, simple, easy to debug, and very efficient (unlike what you are trying to do). You should use indexing.
PS: Your code does not define val, so we have no idea how it relates to your example code or the requested output.
Adam Danz
Adam Danz on 8 Feb 2020
Note #2: this quesiton may have migrated to a new question.

Sign in to comment.

Answers (1)

Sourav Bairagya
Sourav Bairagya on 12 Feb 2020
You can use 'sum' function to compute sum for each row and then can apply 'squueze' function to remove the singleton dimension (i.e. dimension with length 1). After that you can take transpose of the result and you will get the desired output.
val = sum(result,2);
out = squeeze(val);
A = out';
You can leverage these links for further information:

  1 Comment

Guillaume
Guillaume on 12 Feb 2020
Or you can do the squeeze and transpose altogether with just one permute:
A = permute(sum(result, 2) [2 3 1]) %note this do a .' transpose instead of a ' ctranspose. For a logical array the two are the same.

Sign in to comment.

Tags