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The make_figure and add_curve commands can plot data from a file (in both FITS binary and ASCII formats).

1. Two columns: A set of (x,y) points.

   make_figure("file.lis[cols x,y]")
   add_curve("file.lis[cols x,y]")
   

   This will plot up columns x and y from the file file.lis.

2. Three columns: A set of (x,y) points with symmetric errors on y.

   make_figure("file.lis[cols x,y,dy]")
   add_curve("file.lis[cols x,y,dy]")
   

   This will plot up columns x and y from the file file.lis, and draw symmetric error bars whose length is given by the dy column. The dy values should be >= 0.

3. Four columns: A set of (x,y) points with asymmetric errors on y.

   make_figure("file.lis[cols x,y,dylo,dyhi]")
   add_curve("file.lis[cols x,y,dylo,dyhi]")
   

   This will plot up columns x and y from the file file.lis, and draw asymmetric error bars whose lengths are given by the dylo and dyhi columns (which should both be >= 0).

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