Re: FOR statement

[Paul van Delst <paul.vandelst(at)noaa.gov>]

Eli Beckerman wrote:
> 
> Hey,
> 
> I just tried running a FOR loop in the hopes
> of incrementing the variable "i" by steps of 0.25 as follows:
> 
> radius=fltarr(1000)
> FOR i=0.0, 100.0, 0.25 DO BEGIN
> 
>   radius(i)=i
> 
> ENDFOR
> 
> And what I end up with is an array that starts
> with the value 0.75 and is incremented by steps of 1.
> 
> I'm following the convention of the FOR statement as
> presented in IDL's online help. What am I doing wrong?!

Try

  i=-1L
  FOR xi=0.0, 100.0, 0.25 DO BEGIN & i=i+1L & radius(i)=xi & endfor

IDL> print, radius[0:10]
      0.00000     0.250000     0.500000     0.750000      1.00000      1.25000     
1.50000
      1.75000      2.00000      2.25000      2.50000

using i as the array subscript must be converting it to an integer type and screwing stuff
up somehow.

Using loop indices like this should be discouraged, I reckon.

paulv

-- 
Paul van Delst           A little learning is a dangerous thing;
CIMSS @ NOAA/NCEP        Drink deep, or taste not the Pierian spring;
Ph: (301)763-8000 x7274  There shallow draughts intoxicate the brain,
Fax:(301)763-8545        And drinking largely sobers us again.
paul.vandelst@noaa.gov                   Alexander Pope.