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Re: All day FFT.... [message #29206]

Thu, 07 February 2002 01:15

Martin Downing
Messages: 136
Registered: September 1998

Senior Member

"Robert Stockwell" <rgs1967@hotmail.com> wrote in message
news:3C61BC7C.4030904@hotmail.com...
> Paul van Delst wrote:
>
>> Hey there,
>
>
> My guess, regarding slowness, is "Prime Number" (number of points
> in your time series). Try zeropadding up to, or truncating
> down to, a nice factorable number.
>
> I've attached my hackware factors.pro which will return the
> factors of a number. (and its recursive, COOL!)`
>

Hi Bob,
Inspired, I wrote a more compact version of your function which will work on
long64 too
cheers

Martin
ps: probably is already in the jpl/cm/df library anyway!

function ifactors, num, factor_start = factor_start
;+
; Returns the prime factors of an integer
; inspired by Bob Stockwell
; MRD 7/2/2002
;-
maxfac = sqrt(abs(num))
if n_elements(factor_start) eq 0 then begin
if maxfac gt 1073741824 then factor_start = long64(2) else factor_start =
2L
endif
; find the lowest factor and return that plus the result of factoring the
remainder
;stop
for f = factor_start, maxfac do begin
if num mod f eq 0 then begin
return, [f, ifactors(num/f, factor_start = f)]
endif
endfor

; or return if prime
return, [num,1]
end

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[Message index]

		Re: All day FFT.... By: Martin Downing on Thu, 07 February 2002 01:15
		Re: All day FFT.... By: Robert Stockwell on Wed, 06 February 2002 15:30
		prime factors (was Re: All day FFT....) By: Brian Jackel on Fri, 08 February 2002 12:47

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