I have a matrix 16561 x 3. Each row represents a point (x,y,m), and I wanna have a new array or matrix or something that gives me every possible combination of 3 points, So every possible combination of 3 rows (not adding them together).

h = getHeight;

HR=reshape(h,[65341,1])

%turning the h variable into an array [65341 x 1]

x = getX;

XR=reshape(x,[65341,1]);

%turning the x variable into an array [65341 x 1]

y = getY;

YR=reshape(y,[65341,1]);

%turning the y variable into an array [65341 x 1]

FA = [XR YR HR];

%FA stands for Final Array. combines the three variables into one array

indeces=find(FA(:,3)==0);

FA(indeces,:) = [];

%this gets rid of any rows with a 0 in the HR variable.

%now I want every combination of three rows possible from the final array. I don't know how you would represent that.

Also, what would be the best way to reduce the size of the matrix?

[David Goodmanson]

Hi Harrison,

If you really want all possible combinations of 16561 rows taken 3 at a time, that's 16561*16560*16559 / 6 = 7.568847332400000e+11 combinations. That's a lot of combinations. Even if you do a calculation and only store one (double precision) number per combination, it will take approximately 6e12 = 6000 GB of memory. If I have interpreted correctly what you want to do, you may want to rethink this.

[Harrison Chong]

So how could I effectively reduce my matrix to about 300 points?

[Image Analyst]

Area any of the 16,561 values the same? How many unique values are there in those 16,561 numbers? If it's only ten or a hundred or so, it's really easy. If each value is unique, then that's too many values like you and Dave said. You could try to subsample the unique values to get a more manageable number.

[KSSV]

What is the prupose to have every three possible combinations? Are you planning to draw a surface or something? There might be more elegant solution for your problem, if you could tell your purpose.