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Re: gnuplot (fitting of ellipse)

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I have also tried a sample code with x and y values in pnts.dat but I get nan during my fit command and in the end after the plot command I get warning: skipping data file with no valid points. Below are the x y values in pnts.dat

-2.000000   -0.005494
-1.789474   -0.410310
-1.578947   -0.616013
-1.368421   0.760577
-1.157895   0.695609
-0.947368   0.921957
-0.736842   -0.882355
-0.526316   -1.031450
-0.315789   -0.910362
-0.105263   -0.986339
0.105263    -0.897862
0.315789    -1.059766
0.526316    -1.007012
0.736842    0.910494
0.947368    -0.878432
1.157895    0.823232
1.368421    0.831900
1.578947    -0.662069
1.789474    0.427903
2.000000    -0.001474

f(x, y) = x*x + b*x*y + c*y*y + d*x + e*y + f
fit f(x, y) 'pnts.dat' u 1:2:(0) via b,c,d,e,f

set contour
set view map
unset surface
set cntrparam levels discrete 0
set isosamples 1000,1000

set table 'contour.dat'
splot f(x, y)

unset table
unset contour

set terminal pngcairo enhanced
set output 'fig.png'

set xr [-3:3]
set yr [-3:3]
set size square

plot \
    'contour.dat' u 1:2 w l lw 2 lc rgb 'red', \
    'pnts.dat' u 1:2 w p ps 1.5 lc rgb 'black'

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gnuplot (fitting of ellipse) vineeth25396@gmail.com - 2017-03-24 02:24 -0700
  Re: gnuplot (fitting of ellipse) vineeth25396@gmail.com - 2017-03-24 03:01 -0700
    Re: gnuplot (fitting of ellipse) Karl Ratzsch <mail.kfr@gmx.net> - 2017-03-24 12:25 +0100
      Re: gnuplot (fitting of ellipse) vineeth25396@gmail.com - 2017-03-24 17:55 -0700
        Re: gnuplot (fitting of ellipse) Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2017-03-25 14:22 +0100
  Re: gnuplot (fitting of ellipse) Karl Ratzsch <mail.kfr@gmx.net> - 2017-03-24 11:28 +0100

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