Re: Limits to a fitting curve

Stefan Brinker schrieb:
Christoph Bersch schrieb:
Stefan Brinker schrieb:
with the fitting, done like this:
f(x)=a*x**3+b*x**2+c*x+d
a=1; b=1; c=1; d=1
fit f(x) 'test1.DAT' using 1:2 via a,b,c,d
plot [600:1000] 'test1.DAT' using 1:2 title 2, f(x)

Is it possible to set limits to the x-values of the fitting curve? I don´t need the curve to cover the whole 600-1000, only the area of the measured data (630-900) should be covered.
Just change your plot command to
plot [630:900] ...

Christoph

Sadly this is not possible because there are other measuring curves which cover the area of 600:1000 and all graphs have to be from 600 to 1000, so they are comparable.

Ok, now I know what the problem is.

You can do it like this:

f(x)=a*x**3+b*x**2+c*x+d
a=1; b=1; c=1; d=1
fit f(x) 'test1.DAT' using 1:2 via a,b,c,d
F(x) = (x < 630 || x > 900) ? NaN : f(x)
plot [600:1000] 'test1.DAT' using 1:2 title 2, F(x)

However, I don't know if this is the most elegant way.

Isn´t it possible to cut off the fitting curve at some value?

I don't know if it would make sense (and if its possible) to allow a range specification for every function that is plotted and then take the range that includes all 'subranges' to plot the functions:

plot [0:10] f(x), [-2:8] g(x)

gives a plot for [-2:10]

Christoph
.

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