On 25Sep2006, Stefan de Konink wrote:
 I want to plot two contours and a plot with datapoints on top of
 eachother. I got the contours to work with hold on; But when I want to
 plot on top of it with the original datapoints I get the following error:

 gnuplot> sp '/var/tmp/octzU9WJn' u 1:2:3 t "line 1" w lines 1,
 '/var/tmp/octvzTH1t' u 1:2:3 t "line 2" w lines 1, '/var/tmp/octUCFB0C'
 u 1:2 t "" w dots 3, '/var/tmp/octxwitFD' u 1:2 t "" w dots 1

 ^
 line 0: 2 columns only possible with explicit pm3d style (line 5)

 Ofcourse I tryed the explicit style which produced a beautiful gradiant,
 but that is not what I want ;)

 How is this possible?
The contour plot created by gnuplot is done using the 3D mode, so
plotting a set of lines on top of it using the 2D plot functions will
not work.
Possible solutions are to fix gnuplot's contour plotting to be a
modified version of the 2D plotter instead of the 3D plotter or to fix
Octave's contour function to generate the contours and plot them
directly with the 2D plotter. There have been some proposals for
doing the latter but none have yet been incorporated.