set samples <value>
The setting samples determines the number of values along the ordinate axis at which functions are evaluated when they are plotted. For example:
set samples 100
would cause functions to be evaluated at 100 points along the ordinate axis. Increasing this value will cause functions to be plotted more smoothly, but also more slowly, and the PostScript files generated will also be larger. When functions are plotted with the points plot style, this setting controls the number of points plotted.