MATLAB: SUM of selected elements in Matrix

sumuser define

i have matrix

M = [1 1 2 60;

2 3 2 90;

3 1 3 240;

4 2 3 200;

5 3 3 160]

i want to select 1 from 2nd column and acoording to that i want to SUM of 60 and 240. same way i want to select 3 from 2nd column and SUM of 90 and 160.

how to creat?

Best Answer

Are you looking for something like this

M = [1  1  2   60;
    2  3  2   90;
    3  1  3  240;
    4  2  3 200;
    5  3  3 160];
result = splitapply(@sum, M(:,4), M(:,2))

Result

>> result
result =
   300
   200
   250

Related Solutions

MATLAB: Sum elements in a column where there are matching values in an adjacent column

Here's one way, there are probably better ones, but this works:

NEW

A = [1 1 100; 1 2 200; 1 3 50; 2 1 100; 2 2 200; 2 3 50; 3 1 100; 3 2 200; 3 3 50; 3 4 20];
[~,~,idx] = unique(A(:,2)); % Unique second column indices

A3 = A(:,3); % third column values

% Build array with index and cumulative value

idxdv = accumarray(idx,(1:numel(idx))',[],@(x){[sort(x) cumsum(A3(sort(x)))]});
idxdv = cell2mat(cellfun(@(x)[x(:,1), [0;x(1:end-1,2)]],idxdv,'UniformOutput',false))
% Sort it by index and extract second column

dv = sortrows(idxdv);
results = dv(:,2)

OLD, for reference in comments

A = [1 1 100; 1 2 200; 1 3 50; 2 1 100; 2 2 200; 2 3 50; 3 1 100; 3 2 200; 3 3 50; 3 4 20];
[~,~,idx] = unique(A(:,2)); % Unique second column indices
A3 = A(:,3); % third column values
% Build array with index and cumulative value
idxdv = cell2mat(accumarray(idx,(1:numel(idx))',[],@(x){[sort(x) cumsum([0;A3(sort(x(1:end-1)))])]}));
% Sort it by index and extract second column
dv = sortrows(idxdv);
results = dv(:,2)

MATLAB: Arrenging rows and columns

lat   = [-90 -60 -30 00 30 60 90]';
long  = [ -160 -120 -80 -40 00 40 80 120 160 ];
nLat  = length(lat);
nLong = length(long);
both  = [repmat(lat, nLong, 1), repelem(long(:), nLat, 1)];

Alternatively for old Matlab versions, which do not have repelem:

tmp  = repmat(long, nLat, 1);
both = [repmat(lat, nLong, 1), tmp(:)];

Best Answer

Related Solutions

MATLAB: Sum elements in a column where there are matching values in an adjacent column

MATLAB: Arrenging rows and columns

Related Question