Replace numbers in a matrix depending on if statement

Dear all Community members,

I have a 5x5 matrix that contains only numerical values. I want to remove values below a given threshold and add the sum of these values to the next horisontal element that is above the threshold.

My input matrix is as follows:

A=[1 6 7 8 13; 1 3 11 8 15; 1 2 4 13 19; 1 3 4 8 11; 1 3 4 5 11];

Threshold value=5

I.e. I want to replace all values <=5 with zeros and add the sum of these to the next horisontal element that is above the threshold. So the output matrix shall be:

B=[0 7 7 8 13; 0 0 15 8 15; 0 0 0 20 19; 0 0 0 16 11; 0 0 0 0 24];

Can anyone assist me?

Thanks in advance.

Answer 1

[KSSV]

A(A<=5) = 0 

[Askeladden2]

Dear KSSV,

Thank you for the swift reply.

This command will only remove the values below the threshold value. In addition I want to add the sum of these values (<threshold) to the next element (row wise) in the matrix that has a numerical value above the threshold value. I.e. I want the resulting output matrix to be:

B=[0 7 7 8 13; 0 0 15 8 15; 0 0 0 20 19; 0 0 0 16 11; 0 0 0 0 24];

Thank you again for your answer

[KSSV]

A=[1  6  7  8  13; 1  3  11  8  15; 1  2  4  13  19; 1  3  4  8  11; 1  3  4  5  11];
B=[0  7  7  8  13; 0  0  15  8  15; 0  0  0  20  19; 0  0  0  16  11; 0  0  0  0  24];
val = 5 ;
C = A ; 
for i = 1:size(A,1)
  idx = A(i,:)<=val ; 
  id = find(idx) ; 
  C(i,idx) = 0 ; 
  thesum = sum(A(i,idx)) ; 
  C(i,id(end)+1) = thesum+C(i,id(end)+1) ; 
end
C

[Askeladden2]

Dear KSSV,

Thank you very much for all your help!

I have another question, very much related to this problem, but more challenging, which I think you can assist me on.

I have two arrays and 1 matrix;

h=[0.5;1;2;2.5;3];

t=[1 2 3 4 5];

A=[1 6 7 8 13; 1 3 11 8 15; 1 2 4 13 19; 1 3 4 8 11; 1 3 4 5 11];

I want based on a variable threshold matrix, depending on the array h and t, get the same result as above.

for i = 1:size(h)

for j = 1:size(t)

thres(i,j)=3.1*sqrt(h(i))

end

end

Resulting threshold matrix will be:

thresh=[2.2 2.2 2.2 2.2 2.2; 3.1 3.1 3.1 3.1 3.1; 4.4 4.4 4.4 4.4 4.4; 4.9 4.9 4.9 4.9 4.9; 5.4 5.4 5.4 5.4 5.4];

Then I want to apply the same procedure as before, but instead of applying a constant threshold value I want to a threshold matrix. I.e. remove values below the threshold matrix and add the sum of these values (row wise) to the next element that is above the threshold.

Result:

B=[0 7 7 8 13; 0 0 15 8 15; 0 0 0 20 19; 0 0 0 16 11; 0 0 0 0 24];

I can start a new question if this is more convenient.

EDIT: I have created a new post https://se.mathworks.com/matlabcentral/answers/545822-replace-numbers-in-a-matrix-depending-on-if-statements-from-arrays

Thank you in advance.