Round a value to its nearest element in an array.

7Jan2008 Update: I totally rewrote this to use value_locate which gave a factor of 11 speedup based on one test.  Note that to match value_locate I changed the order of the inputs, sorry.

It never fails that you need to do this, especially when you are using cursor.  I finally got fed up with hacking this together each time and wrote this.  I bet it can be improved and perhaps even use histogram, but there are too many gremlins in there for now.

Download: round2array.pro

I will give an example here.

Setup an array of values to find that I want to match

IDL> print, findgen(10)+0.2

     0.200000      1.20000      2.20000      3.20000      4.20000      5.20000      6.20000      7.20000      8.20000      9.20000

print the indices that are the closest elements to my input

IDL> print, round2array(findgen(10)+0.2, [3.4, 3.0, 6.7, 6.3])

           3           3           7           6

and print the values that are the closest

IDL> print, (findgen(10)+0.2)[round2array(findgen(10)+0.2), [3.4, 3.0, 6.7, 6.3]]

      3.20000      3.20000      7.20000      6.20000