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Re: regression with error bars [message #70922 is a reply to message #70719]

Sat, 22 May 2010 06:34

Giuseppe Papa
Messages: 27
Registered: February 2010

Junior Member

Hello,

Thank you for your reply and examples. I am a newbie to IDL and I've never used MPFIT. I read the tutorial from this website:
http://cow.physics.wisc.edu/~craigm/idl/mpfittut.html

and I wrote a pro to fit a line to x and y if we had errors in y only (+/-):

pro test

xval = [1,2,3,4,5]
yval = [1.2,1.9, 3.1, 4.5, 5]
errval = [0.1,0.001,0.1,0.05,0.2]

expr = 'P[0]+P[1]*X' ;line y=A+Bx

result = MPFITEXPR(expr, xval, yval,errval)

plot, xval, yval, psym=2
oplot, xval, result[0]+result[1]*xval

l=linfit(xval, yval) ;no errors considered
oplot, xval, l[0]+l[1]*xval, linestyle=1

end

Are the error values (errval) used in this way in the function MPFITEXPR? And if not, after I calculate the residuals using your method, how do I feed it into the function MPFITFUN ?

Thank you!!

---
frmsrcurl: http://compgroups.net/comp.lang.idl-pvwave/regression-with-e rror-bars

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[Message index]

		regression with error bars By: Meagan Adams on Tue, 04 May 2010 12:57
		Re: regression with error bars By: Craig Markwardt on Tue, 04 May 2010 19:19
		Re: regression with error bars By: Giuseppe Papa on Sat, 22 May 2010 09:44
		Re: regression with error bars By: Craig Markwardt on Sat, 22 May 2010 10:53
		Re: regression with error bars By: Giuseppe Papa on Sat, 22 May 2010 09:29
		Re: regression with error bars By: Craig Markwardt on Sat, 22 May 2010 08:02
		Re: regression with error bars By: Giuseppe Papa on Sat, 22 May 2010 06:34

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