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Re: transforming an array where some values can't [message #10901 is a reply to message #10897]

Fri, 06 February 1998 00:00

offenbrg
Messages: 31
Registered: August 1993

Member

bowler@eisner.decus.org writes:

> I'm trying to write a function that will transform an arbitrary array by taking
> hte natural log of every element in the array.

> What I have is

> function xform, input
> temp = alog(input) ; I realize I could combine these 2 statements
> return, temp ; but it makes debugging easier
> end

> Unfortunately, I can't guarentee that there won't be some elements that are
> zero and thus invalid arguments to alog. what's the "most efficient" way to
> take the alog of any element that's greater than 0 and set the value of ony
> that are less than or equal to 0 to some small value (1e-7 for example)?

I think what you want is this:

function xform, input
temp = alog(input > 1e-7)
return, temp
end

The ">" operator in this case sets a floor on the values of "input"...any
value less than 1e-7 is replaced with 1e-7.

Good luck,
Joel
--
"...And I am unanimous in this" - Mrs. Slocumbe
------------------------------------------------------------ ---------------
| Joel D Offenberg | Joel.D.Offenbrg.1@gsfc.nasa.gov |
| Hughes STX, NASA/GSFC/LASP & STScI | UIT, NGST programmer & sysadmin |

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[Message index]

		Re: transforming an array where some values can't By: Evilio del Rio on Mon, 09 February 1998 00:00
		Re: transforming an array where some values can't By: alpha on Sun, 08 February 1998 00:00
		Re: transforming an array where some values can't By: offenbrg on Fri, 06 February 1998 00:00
		Re: transforming an array where some values can't By: S Penzes on Thu, 05 February 1998 00:00
		Re: transforming an array where some values can't By: meron on Thu, 05 February 1998 00:00

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