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Tag Archives: arrays
A column sort routine
In spreadsheet programs like Excel or LibreOffice, you can apply a sort on a column to every other column in the spreadsheet. IDL’s SORT function doesn’t provide this functionality, but with a little code, we can make it so. The … Continue reading
Dynamically creating variables in a program
There are situations where it may be useful to create variables at runtime in an IDL program, taking the variable names from a string array. Though there are a couple ways of doing this, I’d like to use SCOPE_VARFETCH here, … Continue reading
Posted in data access, language
Tagged arrays, control statements, PNG, SCOPE_VARFETCH, strings
1 Comment
The minimum and maximum operators
Have you used the minimum (<) and maximum (>) operators in IDL? They’re among my favorites; they’re binary operators that return the smaller (minimum) or larger (maximum) of their operands. For example, 5 is larger than 2, so the minimum … Continue reading
Posted in language
Tagged arrays, compound operators, masking, operators, RANDOMN function, WHERE function
3 Comments
An LSD radix sort algorithm in IDL
(Note: I’m at the HDF and HDF-EOS Workshop XV this week, so today I have a guest post by Atle Borsholm, a Senior Consultant in the Exelis VIS Professional Services Group. Atle is an IDL master. I’m trying to persuade … Continue reading
Posted in data analysis, language, programming
Tagged arrays, Atle Borsholm, code performance, guest post, sorting
6 Comments
Converting an indexed image into an RGB image
Here’s an example of how to convert an indexed image into an RGB image. Though they require more memory, I often find RGB images easier to work with because I don’t have to deal with color tables: I invariably forget … Continue reading
Posted in data access, language
Tagged (New) Graphics, arrays, band interleaving, image, PNG
2 Comments
Order of operations in an expression
Given a floating-point array x, which of these two statements: IDL> y1 = 2.0 * x / 3.0 IDL> y2 = x * (2.0 / 3.0) executes faster, the first or the second? Note that both statements produce the same … Continue reading
