Calculating the sum of each row in a matrix.

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.

[Stephen23]

"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:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

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.

[Guillaume]

Note that this is a follow-up to this question

[Adam Danz]

Note #2: this quesiton may have migrated to a new question.

Answer 1

[Sourav Bairagya]

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:

https://www.mathworks.com/help/matlab/ref/squeeze.html

https://www.mathworks.com/help/matlab/ref/sum.html

[Guillaume]

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.