[pstricks] cspline in pst-plot

Patrice MÉGRET Patrice.MEGRET at umons.ac.be
Tue Jul 14 13:14:52 CEST 2015

Dear Luis,

Thanks for this comment.

What I would like to stress is that the blue curve has a discontinuity on the slope and I am not sure it is normal for a cubic spline.
Moreover, if I draw a vertical line around this "discontinuity" the blue curve is no longer single point 

In fact, I would expect a behavior similar to the red curve in the pst-plot example.
In my example, cspline  behaves like curve and vice-versa.

Best regards,

-----Message d'origine-----
De : PSTricks [mailto:pstricks-bounces at tug.org] De la part de Luis Sequeira
Envoyé : mardi 14 juillet 2015 12:54
À : pstricks at tug.org
Objet : Re: [pstricks] cspline in pst-plot

> Dear all,
> I am using pst-plot with cpsline option to draw smooth curves.
> Here are two examples:
> The first one is from the documentation and it works well. (spline in 
> red,  curve in blue) The second one comes from my data and I got a curve (in blue) with a discontinuity (spline in blue, curve in green). Or I was thinking that cubic spline makes the curve without discontinuity up to the second order derivative.
> Is there any trouble in the cspline algorithm or do I make a mistake somewhere?
> Best regards,
> Patrice

You are not making any mistake, and there is no discontinuity. It just happens that the green curve completely covers the blue spline in that particular section.
If you change the order of the two \listplot commands you will see only the blue.
Luis Sequeira

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