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Adding arrays [message #91465]

Fri, 17 July 2015 00:38

Dete van Eeden
Messages: 32
Registered: July 2015

Member

Hallo,

I am trying to add arrays together in a for loop but the end result is just equal to the last array.

for k=0,5 do begin

read in the array etc.

final = final + array

endfor

The final is suppose to be the sum of all the arrays.

Thank you!

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Re: Adding arrays [message #91468 is a reply to message #91465]

Fri, 17 July 2015 02:26

Nikola
Messages: 53
Registered: November 2009

Member

On Friday, July 17, 2015 at 8:39:01 AM UTC+1, Dete van Eeden wrote:
> Hallo,
>
> I am trying to add arrays together in a for loop but the end result is just equal to the last array.
>
> for k=0,5 do begin
>
> read in the array etc.
>
> final = final + array
>
> endfor
>
> The final is suppose to be the sum of all the arrays.
>
> Thank you!

You somehow overwrite your variable f within the loop (if f is reset to 0 for every k, the final result is clearly just the last element). If it is not obvious, perhaps it's in a subfunction that your calling in the loop?

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Re: Adding arrays [message #91471 is a reply to message #91465]

Fri, 17 July 2015 09:42

Dete van Eeden
Messages: 32
Registered: July 2015

Member

Makes sense...

How do I define an array that consists of 5 arrays each with 256x256 elements?

For example final(k) is the sum of the arrays from 1 to 5 and final=fltarr(256,256)

It seems so simple but I cant get it right :-)

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Re: Adding arrays [message #91473 is a reply to message #91471]

Fri, 17 July 2015 11:26

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Dete van Eeden writes:

> How do I define an array that consists of 5 arrays each with 256x256 elements?
>
> For example final(k) is the sum of the arrays from 1 to 5 and final=fltarr(256,256)
>
> It seems so simple but I cant get it right :-)

total = FltArr(256,256)
data = FltArr(256, 256, 5)
FOR j=0,4 do total = Temporary(total) + data[*,*,j]

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")

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Re: Adding arrays [message #91474 is a reply to message #91473]

Fri, 17 July 2015 11:36

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

David Fanning writes:

>
> Dete van Eeden writes:
>
>> How do I define an array that consists of 5 arrays each with 256x256 elements?
>>
>> For example final(k) is the sum of the arrays from 1 to 5 and final=fltarr(256,256)
>>
>> It seems so simple but I cant get it right :-)
>
> total = FltArr(256,256)
> data = FltArr(256, 256, 5)
> FOR j=0,4 do total = Temporary(total) + data[*,*,j]

Or, the IDL Way:

data = Randomu(seed, 256,256,5)
total = Total(data, 3)

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")

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Re: Adding arrays [message #91480 is a reply to message #91474]

Sun, 19 July 2015 05:34

Dete van Eeden
Messages: 32
Registered: July 2015

Member

Thank you very much :-)

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Re: Adding arrays [message #91481 is a reply to message #91480]

Mon, 20 July 2015 00:34

dete.liebenberg
Messages: 1
Registered: July 2015

Junior Member

On Sunday, July 19, 2015 at 2:34:32 PM UTC+2, Dete van Eeden wrote:
> Thank you very much :-)

Is there a reason why this would work for 3 dimensions but not 2.

If a have data=fltarr(256,4)

the total is equal to the last array again?

Thank you

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