Find elements from a matrix and sum variables from other matrix

Hi,

I have a matrix of lat long (406, 964) say A, and B. I also have a huge matrix of length 36000 and 3 variables (lat, long, intensity), say C. The lat lon in C have repeated values. I need to find only the elements of A and B that match in C, but also sum the intensity values of all those matching coordinates.

Thank you. Look forward to you help.

Answer 1

[Matt J]

T=array2table(C);
Gs = groupsummary(T,{'C1','C2'},@sum);
Gs = table2array(Gs(:,[1,2,4]));

bool=ismember(Gs(:,1),A) & ismember(Gs(:,2),B);

result=Gs(bool,:),

[nlm]

array2table and group summary did the trick I was looking for. Thanks alot.

[nlm]

I have a matrix of lat lon count, where for same lat lon, the count variable range between 1 to 4.

I need to have something like this,

LAT LON cnt = 1 cnt=2 cnt=3 cnt =4

12.4 91.4 1 0 3 0

31.4 45.6 2 4 0 9

45.9 91.5 10 0 9 20

I tried table, I could not figure out.

Answer 2

[Matt J]

Na=numel(A);
Nb=numel(B);

[~,Ia]=ismember(C(:,1),A(:));
[~,Ib]=ismember(C(:,2),B(:));

result = accumarray([Ia,Ib],C(:,3),[Na,Nb]);

[nlm]

This issued an error,

"Error using accumarray

Requested 391384x391384 (1141.3GB) array exceeds maximum array size preference."