[ncl-talk] populating lists with multidimensional arrays

[Wei Huang]

Will,

You’d better use (the sample) list this way:

P = NewList("fifo")           ;create new list
Q = NewList("fifo")          ;another new list
x = (/(/1,2,3/),(/4,5,6/)/)  ;a test array

do i = 0, 2

   ListAppend(P,(/x/))             ;keep adding array 'x'
   ListAppend(Q,(/x(:,:i)/))       ;add a different sized subset of 'x'

end do

print(P[1])
print(Q[0])

Wei Huang

From: ncl-talk-bounces at ucar.edu [mailto:ncl-talk-bounces at ucar.edu] On Behalf Of Rick Brownrigg
Sent: Wednesday, March 02, 2016 11:25 PM
To: Will Hobbs
Cc: ncl-talk at ucar.edu
Subject: Re: [ncl-talk] populating lists with multidimensional arrays

Hi Will,
It looks like you've uncovered a bug, and it seems to relate to the array-slicing in combination with the list. If I manually create a list comprised of different sized arrays, it works:
    l = [/ (/ 1, 2, 3 /), (/ 4, 5, 6, 7, 8 /) /]
    print(l)
But if we take a condensed version of your example:
We get:

    ListAppend(Q,x(:,:2))
    print(Q)


    Variable: Q
    Type: list
    Total Size: 4 bytes
                1 values
    Number of Dimensions: 1
    Dimensions and sizes:   [1]
    Coordinates:
    Type: list <fifo>
    Total items: 0
which is clearly not right. I tried assigning the slice of the x-array to a temporary variable and then appending the temp-var to the list, but that does not work either.

I will file a bug-report ticket in the morning and take a look at what is going on. I'm sorry that I don't have a good work-around offhand.
Rick

On Wed, Mar 2, 2016 at 7:56 PM, Will Hobbs <will.hobbs at utas.edu.au<mailto:will.hobbs at utas.edu.au>> wrote:
Hi all

My understanding from the documentation is that elements of an NCL list do not need to be the same size, but I am having trouble populating a list with arrays that are not the same size.

Consider the following test case:

P = NewList("fifo")           ;create new list
Q = NewList("fifo")          ;another new list
x = (/(/1,2,3/),(/4,5,6/)/)  ;a test array

do i = 0, 2

ListAppend(P,x)                 ;keep adding array 'x'
ListAppend(Q,x(:,:i))       ;add a different sized subset of 'x'

end do

print(P)

;returns the following (expected)
;Variable: P
;Type: list
;Total Size: 4 bytes
;            1 values;
;Number of Dimensions: 1
;Dimensions and sizes:   [1]
;Coordinates:
;Type: list <fifo>
;Total items: 3


print(Q)
;returns the following (an empty list)Variable: P
Type: list
Total Size: 4 bytes
            1 values
Number of Dimensions: 1
Dimensions and sizes:   [1]
Coordinates:
Type: list <fifo>
Total items: 0

What am I missing here?

Many thanks

Will


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