[ncl-talk] index lists in assignment

[Axel Seifert]

Maybe I should add that the output of my little script is


(0)      0 0
(1)      3 4
(2)      2 2


This is with NCAR Command Language Version 6.3.0


The variables x and y are


Variable: x
Type: float
Total Size: 12 bytes
             3 values
Number of Dimensions: 1
Dimensions and sizes:   [3]
Coordinates:
Number Of Attributes: 1
   _FillValue :  9.96921e+36
(0)      0
(1)      3
(2)      2

Variable: y
Type: float
Total Size: 12 bytes
             3 values
Number of Dimensions: 1
Dimensions and sizes:   [3]
Coordinates:
Number Of Attributes: 1
   _FillValue :  9.96921e+36
(0)      0
(1)      4
(2)      2



Am 24.11.2018 um 15:16 schrieb Seifert Axel:
>
>
> Hi,
>
>
> I have a somewhat unexpected behavior when using index lists. Here a 
> simplified example:
>
>
>   x = new( 3, float)
>   x = 0.0
>   y = x
>   z = (/1.,2.,3./)
>   idx = (/1,2,1/)
>   x(idx) = x(idx) + z
>
>   do i=0,dimsizes(idx)-1
>     y(idx(i)) = y(idx(i)) + z(i)
>   end do
>
>   print(" "+x+" "+y)
>
> I would have expected that x and y end up being the same, but they are 
> not. The double assignment to index 1 does not work for the vector 
> assignment. Is this the intended behavior for arrays in ncl?
>
> How can I get the 2nd behavior and still avoid the do-loop?
>
> In my case I am assigning measured values from satellite overpasses to 
> a global grid and it can of course happen that I have multiple 
> overpasses for a grid point in an observation vector. Hence, in 
> addition to the sum of the values I would count the number of overpasses
>
>   cnt = (/0,0,0/)
>   cnt(idx) = cnt(idx) + 1
>   print(" "+cnt)
>
> and then xavg = x/cnt should give me the proper average for, for 
> example, one hour of data. What I need in the end is the correct 
> average for xavg and the number of measurements used at each grid point.
>
> Thanks in advance for any helpful comments and suggestions.
>
> Axel
>
>
>
>
>
>
>
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