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Multi-column sort [message #79404]

Thu, 01 March 2012 07:02

Percy Pugwash
Messages: 12
Registered: January 2012

Junior Member

I would like to sort a 2D string by column, specifying primary,
secondary and further sort criteria (i.e. rows which are equal based
on criterion 1 are sorted by criterion 2).

Is there any neat way to do this in IDL?

I'd thought of using the following:

tosort = [3,1,5] ; Sort by column 3, then 1, then 5
maxlen = max(strlen(sortarray[tosort,*])) ; Length of longest string
paddedarray =
string(sortarray[tosort,*],format='(a'+string(maxlen,format= '(i0)') +
')' ) ; Pad all strings to match longest length
concatarray = paddedarray[0,*]
for i = 0, n_elements(tosort)-1 do concatarray += paddedarray[i,*] ;
Concatenate strings across columns
indices = sort(concatarray) ; Sort the concatenated strings

However, this method does not allow me to specify which direction the
sort should go for each of the sort columns. Can anyone think of a way
to extend the method to allow this (or a completely different method
which achieves the same effect!)?

Thanks,

P

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[Message index]

		Multi-column sort By: Percy Pugwash on Thu, 01 March 2012 07:02
		Re: Multi-column sort By: Percy Pugwash on Mon, 05 March 2012 02:59
		Re: Multi-column sort By: Brian Wolven on Mon, 05 March 2012 09:54
		Re: Multi-column sort By: Percy Pugwash on Mon, 05 March 2012 02:53
		Multi-column sort By: cgguido on Fri, 02 March 2012 04:26
		Re: Multi-column sort By: wlandsman on Thu, 01 March 2012 14:02

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