I have to add the values that are inside the matrix called s

s= [...
99  99  0.100  0.120  0  0.500  0;
0       0  0       0       0.150   0.120   0;
0.110  0.010  0.010  0  0  0.300  0.100;
0  0.250  0  0.050  0.060  0.100  0.110;
0  0.120  0.040  0  0.500  0.750  1.200];

I have a file with different matrices. I want to write a general code that will add all the values inside this matrix without including the last two in this case 0.750 1.200 and the 99's

so far I have

r=(s(1:5,1:7))
y=sum(r(r<99))

I don't know to remove the last two values as in a general code that will work for the rest of the matrices.

[Azzi Abdelmalek]

what is the size of your matrix s, If you remove two elements, how can you save s in a new matrix?

[marie]

the matrix contains 10 rows and 7 columns

[Azzi Abdelmalek]

What do you mean by and the 99's

[marie]

as in don't include the 99's, remove them

Answer 1

[Image Analyst]

Close. But try it this way if you want to sum everything, except for the last two elements in the last row (kind of a weird restriction, but whatever...), that is less than 99. The key is the transpose which you forgot to do, because if you just do (:) it goes down rows in a column first before it moves over to the next column.

clc;
format compact
format longg
s= [...
99  99  0.100  0.120  0  0.500  0;
0       0  0       0       0.150   0.120   0;
0.110  0.010  0.010  0  0  0.300  0.100;
0  0.250  0  0.050  0.060  0.100  0.110;
0  0.120  0.040  0  0.500  0.750  1.200];
sTransposed = s';  % Note the transpose.
% Get all but the last two columns in the last row.
allButLast2 = sTransposed(1:end-2)  
% Now threshold at 99 and sum those below the threshold.
y=sum(allButLast2(allButLast2<99))

The answer:

y =
     2.75

[marie]

yes the answer is correct... Tank you

[marie]

what if I want to remove the first 5 elements of the matrix s after the transpose?

[Image Analyst]

The first 5 elements after the transpose would be the first 5 rows in column 1 but not including the last two elements in column1 of sTransposed. Remember, MATLAB's linear indexing goes down rows in a column first before moving over to the next column, so the first 5 after transposing is sTransposed(1:5, 1). You can extract them to a new array, but you can't remove (delete/eliminate) them unless you convert sTransposed to a cell array.