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outputgnuplotsmoothing

How to output smooth cspline curve as a data file

Does anybody know how to extract some data of smooth cspline curve for a given data?

For instance, there is a data file which has 2 columns corresponding to x and y values. I can draw the data with smooth cpline curve by the following commands

p 'data' w lp, ""  smooth csplines

I want to extract the smooth cpline curve as an another data file.

Solution

  • This can be done by setting a table. Consider the following data file:

    0 1
1 2
2 3
3 2
4 2
5 4
6 8
7 5
8 3
9 1

    The data itself and its csplines interpolation look like this:

    enter image description here

    To print the interpolation to a table one does the following:

    set samples 100
set table "table_100"
plot "data" smooth csplines
set samples 20
set table "table_20"
plot "data" smooth csplines
unset table

    set samples determines the number of points used to construct the spline curve. And you can visualize it:

    set key left
plot "data" pt 7 t "Original data", \
     "table_100" w l t "Splines (100 samples)", \
     "table_20" w l t "Splines (20 samples)"

    enter image description here