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Re: simple array math question [message #33817 is a reply to message #33701]

Fri, 24 January 2003 04:43

Pepijn Kenter
Messages: 31
Registered: April 2002

Member

"Craig Markwardt" <craigmnet@cow.physics.wisc.edu> wrote in message
news:onwul4cu8t.fsf@cow.physics.wisc.edu...
>
> Heinz Stege <reply_to_posting@arcor.de> writes:
>> On Thu, 16 Jan 2003 14:05:27 -0600, "Sean Raffuse" <sean@me.wustl.edu>
>> wrote:
>>
>>>> > a=[[1,2,3],[4,5,6],[7,8,9]]
>>>
>>>> > b=[1,2,3]
>>>
>>> What is the best (read, fastest) way to multiply b by each individual
row of
>>> a? I would like to return a result of:
>>>
>>> [[1,4,9],[4,10,18],[7,14,27]]
>>
>>
>> result=a*b(*,intarr(3))
>
> WOW! I've never seen that! It scares me how cool that is. :-)

That is mighty cool indeed! Is that documented somewhere?

And does any IDL-wizard know a similar trick to average each row/column of
a?
i.e. to replace the following lines:

result = dblarr(3)
for i = 0, 2 do result[i] = mean(a[*,i])

I don't think it's possible, but who knows.

Pepijn Kenter.

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[Message index]

		Re: simple array math question By: marc schellens[1] on Sun, 19 January 2003 22:55
		Re: simple array math question By: Jeff Guerber on Fri, 17 January 2003 20:21
		Re: simple array math question By: Heinz Stege on Fri, 17 January 2003 16:51
		Re: simple array math question By: Sean Raffuse on Fri, 17 January 2003 14:10
		Re: simple array math question By: JD Smith on Fri, 17 January 2003 13:46
		Re: simple array math question By: Craig Markwardt on Thu, 16 January 2003 19:47
		Re: simple array math question By: Heinz Stege on Thu, 16 January 2003 16:26
		Re: simple array math question By: Craig Markwardt on Thu, 16 January 2003 13:30
		Re: simple array math question By: Pepijn Kenter on Fri, 24 January 2003 04:43
		Re: simple array math question By: JD Smith on Thu, 23 January 2003 08:53
		Re: simple array math question By: Heinz Stege on Sun, 26 January 2003 11:25
		Re: simple array math question By: Jeff Guerber on Sat, 25 January 2003 01:12

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