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CURVEFIT [message #39647]

Wed, 02 June 2004 08:26

Andreas Ernst
Messages: 14
Registered: July 2002

Junior Member

Hi,

(1) I am using CURVEFIT to fit a straight line
through my data points. My user-supplied
function looks like this:

PRO gerade, X, A, F, PDER
F=A[0]+A[1]*X
IF N_PARAMS() GE 4 THEN $
PDER = [[REPLICATE(1.0, N_ELEMENTS(X))], [X]]
RETURN
END

Anyway, even though it defines a straight line,
the routine CURVEFIT seems to fit some other
curve through the data points, which is something
else than a straight line, maybe a higher-order
polynomial. What is the reason for this?

(2) I had problems with fitting data points with
polynomials higher than third order, like fourth
or fifth order. Is this problem known?

Thanks in advance. Andreas

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