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Re: How can I integrate? (easy question?) [message #147 is a reply to message #2]

Mon, 25 March 1991 09:33

ramesh
Messages: 7
Registered: February 1991

Junior Member

In article <1991Mar20.233728.1@csc.anu.edu.au> bdb112@csc.anu.edu.au writes:
> How can I efficiently do a running sum of a vector (integrate)? The explicitly
> coded version (IDL v2)
> for i=1,n-1 x(i)=x(i) + x(i-1) achieves the desired effect, but takes (VS3100)
> 1 second for a 2000 element array compared to .01 sec for z=x+x, a similar
> number of operations. This is such an obvious thing to do that I must be
> missing something obvious - I can't find it in the userlib either (just
> deriv).

Assuming "i" represents the current array index value upto which you want to
sum the elements of the array "x", try:

sum_x = total(x(0:i))

or a variation thereof. The dimension of array "sum_x" will be automatically
dimensioned to the value contained in "i"

Note: Function "total" is a PV Wave system routine.

R.V.

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[Message index]

		How can I integrate? (easy question?) By: bdb112 on Wed, 20 March 1991 04:37
		Re: How can I integrate? (not so easy?) By: bdb112 on Mon, 25 March 1991 12:18
		Re: How can I integrate? (easy question?) By: ramesh on Mon, 25 March 1991 09:33
		Re: How can I integrate? (easy question?) By: bruce on Thu, 21 March 1991 16:22

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