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Re: For..Do Loop and If statements [message #94100 is a reply to message #94098]

Thu, 19 January 2017 02:44

Markus Schmassmann
Messages: 129
Registered: April 2016

Senior Member

On 01/19/2017 10:06 AM, Helder wrote:
> That should then work. However, IDL is not made for loops. The
> typical way to do this is to use the where function
> (http://www.harrisgeospatial.com/docs/WHERE.html):
>
> b2 = a[where(a gt 5)]
>
> if you're not sure if any elements of a are greater than 5, then you
> should use: pos = where(a gt 5, cnt) if cnt gt 0 then b2 = a[pos]
> else b2 = []
A small addition to Helder's answer:
if there might be elements greater than 5, you could also use:

b2 = a[where(a gt 5,/NULL)]

this avoids the use of if...then, which is rather slow in IDL

Markus

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[Message index]

		For..Do Loop and If statements By: smnadoum on Wed, 18 January 2017 21:18
		Re: For..Do Loop and If statements By: Helder Marchetto on Thu, 19 January 2017 01:06
		Re: For..Do Loop and If statements By: Markus Schmassmann on Thu, 19 January 2017 02:44
		Re: For..Do Loop and If statements By: Heinz Stege on Thu, 19 January 2017 09:43

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