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what am I doing wrong? [message #3602]

Thu, 16 February 1995 16:09

babaka
Messages: 3
Registered: February 1995

Junior Member

Dear Netters,

I'm trying to plot the funtion:

f(x)=x*log(x/w)-x (x>0,w>0)

using PV~WAVE.

I know that this function has a minimum at x=w.

To see this, note that

f`(x)=log(x/w)

Setting f`(x)=0 gives x=w. On the other hand:

f``(x)=1/x > 0 for all x

Therefore x=w is the minimum.

THE PROBLEM IS that when I plot this function in PV~WAVE
the minimum appears at another point.

I'm using the following set of commands:

WAVE> w=5.0
WAVE> x=INDGEN(400)
WAVE> x=x+0.1 + 0.01 ; x goes from 0.01 to 40.01
WAVE> fx=x*ALOG10(x/w)-x
WAVE> PLOT,x,fx

I would appreciate if you would tell me what I'm doing
wrong?

Regards,
Babak

--
Babak A. Ardekani babaka@atom.ansto.gov.au
Dept. of Nuclear Medicine phone: +61-2-516-8011
Royal Prince Alfred Hospital fax: +61-2-550-5172
Missinden Rd., Camperdown, NSW 2050 AUSTRALIA

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[Message index]

		what am I doing wrong? By: babaka on Thu, 16 February 1995 16:09
		Re: what am I doing wrong? By: thompson on Tue, 06 October 1998 00:00
		Re: what am I doing wrong? By: steinhh on Tue, 06 October 1998 00:00
		Re: what am I doing wrong? By: Bruce Bowler on Tue, 06 October 1998 00:00
		Re: what am I doing wrong? By: thompson on Mon, 05 October 1998 00:00
		Re: what am I doing wrong? By: Bruce Bowler on Mon, 05 October 1998 00:00
		Re: what am I doing wrong? By: Jeffrey Newmark on Mon, 05 October 1998 00:00
		Re: what am I doing wrong? By: Bruce Bowler on Tue, 06 October 1998 00:00

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