|
|
| Re: Pasting subarray into array with compound assignment [message #53601 is a reply to message #53596] |
Fri, 20 April 2007 14:34   |
Vince Hradil
Messages: 574
Registered: December 1999
|
Senior Member |
|
|
On Apr 20, 12:29 pm, hradilv <hrad...@yahoo.com> wrote:
> On Apr 19, 7:37 pm, "m.avd...@gmail.com" <m.avd...@gmail.com> wrote:
>
>> i'm trying to use the advantage of "+=" when reshaping 2d array to 1d
>
>> Can anyone tell me why the following produce different values?
>> (difference in shape and type of the results is not a problem)
>
>> a1=indgen(3,7) & for i=0,2 do a2[0,i*2]+=a1[i,*] & print,a2
>
>> a1=indgen(3,7) & a2=intarr(3,11) & for i=0,2 do a2[i,i*2]=a1[i,*] &
>> a2=total(a2,1) & print,a2
>
>> thanks,
>> max
>
> Decompose the += into a2[0,2] = a2[0,2] + a1[1,*] (for i=1, for
> instance).
>
> The RHS is 6 + a1[1,*] which is transpose(7,10,13,16,19,22,25). This
> then gets placed into the a2 array at position [0,2]
>
> Same for i=2...
This will work:
a1=indgen(3,7) & a2=intarr(3,11) & for i=0,2 do
a2[0,i*2:i*2+7-1]+=a1[i,*] & print,a2
|
|
|
|
| Re: Pasting subarray into array with compound assignment [message #53609 is a reply to message #53601] |
Fri, 20 April 2007 10:29 |
Vince Hradil
Messages: 574
Registered: December 1999
|
Senior Member |
|
|
On Apr 19, 7:37 pm, "m.avd...@gmail.com" <m.avd...@gmail.com> wrote:
> i'm trying to use the advantage of "+=" when reshaping 2d array to 1d
>
> Can anyone tell me why the following produce different values?
> (difference in shape and type of the results is not a problem)
>
> a1=indgen(3,7) & for i=0,2 do a2[0,i*2]+=a1[i,*] & print,a2
>
> a1=indgen(3,7) & a2=intarr(3,11) & for i=0,2 do a2[i,i*2]=a1[i,*] &
> a2=total(a2,1) & print,a2
>
> thanks,
> max
Decompose the += into a2[0,2] = a2[0,2] + a1[1,*] (for i=1, for
instance).
The RHS is 6 + a1[1,*] which is transpose(7,10,13,16,19,22,25). This
then gets placed into the a2 array at position [0,2]
Same for i=2...
|
|
|
|
| Re: Pasting subarray into array with compound assignment [message #53729 is a reply to message #53596] |
Mon, 23 April 2007 09:25 |
Vince Hradil
Messages: 574
Registered: December 1999
|
Senior Member |
|
|
On Apr 21, 8:21 am, "m.avd...@gmail.com" <m.avd...@gmail.com> wrote:
> Thanks a lot, Vince!
> It works indeed, although i still don't understand why my code didn't.
> According to the manual, only a starting point is needed for pasting
> an array into another one...
That's true - only a "starting point" is needed when pasting. The
problem is that when you use the += assigment, the starting point is
"translated" to a scalar, i.e. the value at that starting point. The
sum of the scalar with the vector is then pasted at the starting point.
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
