| Re: Array definition [message #55271] |
Wed, 08 August 2007 10:53 |
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Bob[3]
Messages: 60
Registered: December 2006
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Member |
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On Aug 8, 1:38 pm, Conor <cmanc...@gmail.com> wrote:
> On Aug 8, 1:18 pm, Yaswant Pradhan <Yaswant.Prad...@gmail.com> wrote:
>> avoid FOR loop, use WHERE
>> indices = where(array GT value, n_wh)
>
> specifically:
>
> array_size = size(array1, /dimensions)
> array2 = fltarr(array_size)
> w = where( array1 gt value, c )
> if c gt 0 then array2[w] = array1[w]
w will be an array of the indices, sized to the number of elements of
array1 gt value (given by c), which is what Melanie was looking for
afaict.
array2 will be the same size as array1, but will have masked out any
elements le value. (mask should be 0.0).
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| Re: Array definition [message #55273 is a reply to message #55271] |
Wed, 08 August 2007 10:38  |
Conor
Messages: 138
Registered: February 2007
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Senior Member |
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On Aug 8, 1:18 pm, Yaswant Pradhan <Yaswant.Prad...@gmail.com> wrote:
> On Aug 8, 6:00 pm, Melanie <mkjone...@gmail.com> wrote:
>
>> Hi,
>> I am trying to check an array of about 19000 elements for values that
>> are above a certain value. I then want to save only the index of the
>> larger values in a new array.
>
> avoid FOR loop, use WHERE
> indices = where(array GT value, n_wh)
>
>
>
>> So, I am going through the original array with a for loop and checking
>> if each value is greater than 19:
>> for i=0, nelements-1 do begin
>> if (array1[i] gt 19) then...
>
>> Next, if the value in array1 is in fact greater than 19, I want to
>> save the value of i into a new array such as
>
>> if(array1[i] gt 19) then array2[...]=i
>
>> But I'm not sure how to make this work such that I can write each
>> subsequent i value for which the value in array1 is gt 19 into each
>> subsequenbt space in array2...
>
>> Any ideas? Please let me know if this question is not clear...
specifically:
array_size = size(array1, /dimensions)
array2 = fltarr(array_size)
w = where( array1 gt value, c )
if c gt 0 then array2[w] = array1[w]
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| Re: Array definition [message #55275 is a reply to message #55273] |
Wed, 08 August 2007 10:18 |
yp
Messages: 42
Registered: February 2005
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Member |
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On Aug 8, 6:00 pm, Melanie <mkjone...@gmail.com> wrote:
> Hi,
> I am trying to check an array of about 19000 elements for values that
> are above a certain value. I then want to save only the index of the
> larger values in a new array.
avoid FOR loop, use WHERE
indices = where(array GT value, n_wh)
>
> So, I am going through the original array with a for loop and checking
> if each value is greater than 19:
> for i=0, nelements-1 do begin
> if (array1[i] gt 19) then...
>
> Next, if the value in array1 is in fact greater than 19, I want to
> save the value of i into a new array such as
>
> if(array1[i] gt 19) then array2[...]=i
>
> But I'm not sure how to make this work such that I can write each
> subsequent i value for which the value in array1 is gt 19 into each
> subsequenbt space in array2...
>
> Any ideas? Please let me know if this question is not clear...
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| Re: Array definition [message #55276 is a reply to message #55275] |
Wed, 08 August 2007 10:15 |
Bob[3]
Messages: 60
Registered: December 2006
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Member |
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On Aug 8, 1:00 pm, Melanie <mkjone...@gmail.com> wrote:
> Any ideas? Please let me know if this question is not clear...
Look at the WHERE command.
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