Statistics - Two dimensional frequency analysis
Statistics - Two dimensional frequency analysis
(OP)
I have 250000 samples of data, in 2 dimensions (ie x,y). I need to plot the frequency distribution in two dimensions, ie split the xy plane up into little squares and count the number of points in each square. I have no problem plotting that, I just can't find a way of easily generating the 2 dimensional histogram.
This must be a common problem, yet Minitab, Scilab and R do not do it easily, that I can find. I can do it in Excel, but run into problems with the number of points, and it is messy anyway.
Is there a free program available for this? Failing that, what is the proper term for this sort of analysis? Another option would be to use Matlab if you know of a script.
This must be a common problem, yet Minitab, Scilab and R do not do it easily, that I can find. I can do it in Excel, but run into problems with the number of points, and it is messy anyway.
Is there a free program available for this? Failing that, what is the proper term for this sort of analysis? Another option would be to use Matlab if you know of a script.
Cheers
Greg Locock





RE: Statistics - Two dimensional frequency analysis
How many boxes are you splitting the data into? Is it in a text file? A VBA routine in excel would be easy enough to write, and it wouldn't require holding all the data simultaneously within a spreadsheet (although if you have few enough boxes, the spreadsheet might be a good place for the output).
RE: Statistics - Two dimensional frequency analysis
"You can read ASCII data separated with spaces into a two column vector,
V, of
x,y pairs, (250000 of them) then create, say, a 100 by 100 matrix by
saying
V:=READPRN(data)
i:=0;rows(V)
M sub 100,100 := 0
This will initialize all elements to 0 automatically.
M sub ( V sub 0,i, V sub 1,i) = M sub ( V sub 0,i,V sub1,i)+ 1"
Sneaky!
Excel bombs out if you try and fully populate a worksheet, as my solution needed to.
Cheers
Greg Locock
RE: Statistics - Two dimensional frequency analysis