Calculate median values of slices of array associated with histogram bins

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dormant
dormant 2023-11-15
评论： Star Strider 2023-11-15
I have an array (array1) which I want to put into histogram bins. I have a second array (array2) which is the same length.
I can sum the values of array2 in each bin with this:
[count, edges, idx] = histcounts(array1,edges);
binsums = accumarray(idx,array2);
But how can I calculate the median values of array2 in each bin?

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采纳的回答

Star Strider
Star Strider 2023-11-15
Ran in:
I would use another accumarray call:
binmedians = accumarray(idx+1, (1:numel(idx)).', [], @(x)median(array2(x)))
Creating data and correcting for ‘idx’ having 0 for some elements (making them inappropriate index values) —
array1 = randn(1E+3,1);
array2 = randn(1E+3,1);
edges = 1:9;
[count, edges, idx] = histcounts(array1,edges);
binsums = accumarray(idx+1,array2)
binsums = 4×1
-13.0331 20.8357 -1.5279 -2.0722
binmedians = accumarray(idx+1, (1:numel(idx)).', [], @(x)median(array2(x)))
binmedians = 4×1
-0.0237 0.2213 0.1113 -1.0361
.
  2 个评论
dormant
dormant 2023-11-15
Thank you very much. Some of the values going into the median ar NaNs, but I can handle them.
Star Strider
Star Strider 2023-11-15
As always, my pleasure!
Use the missingflag option that works best for you.
One such:
binmedians = accumarray(idx+1, (1:numel(idx)).', [], @(x)median(array2(x),'omitmissing'))
There are several others.
.

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更多回答（1 个）

Steven Lord
Steven Lord 2023-11-15
I would use the groupsummary function with the grouping information from the idx variable.
If all you want is the bin numbers, you could also use the discretize function instead of histcounts.

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