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Re: Mode function for floating point arrays [message #85224 is a reply to message #85131]

Wed, 17 July 2013 07:08

Rob Klooster
Messages: 18
Registered: February 2013

Junior Member

Op dinsdag 9 juli 2013 15:36:46 UTC+2 schreef Matthew Argall het volgende:
> It seems like VALUE_LOCATE and HISTOGRAM solutions would have large limitations. The bin size for HISTOGRAM would have to be "2*epsilon", which would rule out data with a large dynamic range. Also, the bin should be centered on the data point so that two points falling within "epsilon" of one another do not get separated because the bins are offset.

The case of a large dynamical range is precisely the reason why I used VALUE_LOCATE instead of a plain HISTOGRAM with binsize set. Define the function like this:

function mode, array
sortedarray = array[Sort(array)]
arrayenum = sortedarray[Uniq(sortedarray)]
mappedarray = Value_Locate(arrayenum, array)
hist = histogram(mappedarray, min=0)
return, arrayenum[where(hist eq max(hist))]
end

Example:
print, mode([1., 10.^8, 10.^8])
1.00000e+008
print, mode([10.^8, 10.^8+1, 1.])
1.00000e+008
print, mode([10.^8, 10.^8+10, 1.])
1.00000 1.00000e+008 1.00000e+008

So in this case the machine precision is about 7 significant digits, as expected for floats. Note that two floats are only assumed equal when they have the exact same binary value.

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[Message index]

		Mode function for floating point arrays By: Matthew Argall on Fri, 05 July 2013 11:55
		Re: Mode function for floating point arrays By: Rob Klooster on Mon, 08 July 2013 01:01
		Re: Mode function for floating point arrays By: Rob Klooster on Mon, 08 July 2013 01:24
		Re: Mode function for floating point arrays By: Matthew Argall on Tue, 09 July 2013 06:36
		Re: Mode function for floating point arrays By: David Fanning on Tue, 09 July 2013 07:01
		Re: Mode function for floating point arrays By: Rob Klooster on Wed, 17 July 2013 07:08
		Re: Mode function for floating point arrays By: Matthew Argall on Fri, 19 July 2013 16:50
		Re: Mode function for floating point arrays By: Rob Klooster on Mon, 22 July 2013 04:24

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