Problem 2029. Convert vector datasets to plot with imagesc instead of scatter

Ted

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For large datasets this allows much faster plotting.
An irregular 2D spatial sampling is provided in x and y vectors with a data point to plot in vector d. A bin size is also provded in vector b=[dx,dy]
Return a 2D matrix M with minimal empty cells with the correct spatial relationship of d and last value only retained in the event of duplicates.
Example
 b = [6,9];
 x = rand(3333,1)*100*b(1)+1500;
 y = rand(3333,1)*100*b(2)+50000;
 d = sind(sqrt(x.^2+y.^2))./sqrt(x.^2+y.^2);
Return G, a 2D matrix with d binned in rows and columns

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Last Solution submitted on May 27, 2026

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Sean de Wolski on 3 Dec 2013

I think the test suite is wrong:

If "G" is supposed to have a "minimal number of empty cells" then why is the second test a 9x9 with the last column being all zeros? I would expect this column to be unnecessary.

For the first test, I'm getting 1.2690e-05 for chk2.

Problem is great though!

Ted on 4 Dec 2013

Sean, I agree, my bad, I removed the end column and rescored. my code yields 1.2680e-05 still (last value kept per cell?)

Rafael S.T. Vieira on 15 Oct 2020

The function roundn is no longer supported by Cody, please update the test suite to round(x/10^e)*10^e.

goc3 on 27 Oct 2020

The test suite has been fixed as requested by Rafael S.T. Vieira.

Rafael S.T. Vieira on 30 Oct 2020

Thanks, goc3. Now the problem is working again. :)

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