Draw a ring segment in GNUPlot

Question

I would like to obscure a specific plot in the polar plot using GNUPlot. This area is limited by the limits in R (r1, r2) and Theta (t1, t2), so the final shape is a segment of the ring defined by only 4 points in the polar space.

In Cartesian graphics, it is fairly easy to draw a rectangle, either (set object rect) or a filledcurve with four vertices. However, the filled shape curve defined by four points in the polar graph still leads to quadrangularity (lines with constant R should be circular arcs, not straight).

Is there a simple or simple way to plot this shape in polar coordinates? I tried using two arcs and then filled the space between them, but so far this does not work, and I'm not sure if there is a better way to do this.

Answer 1

Unfortunately, this is not so simple. You can set the circle object for which you specify the start and end angles. To cut out the center part, you should draw a second white circle above:

 set xrange [-1:1] set yrange [-1:1] set size ratio -1 r1 = 0.5 r2 = 1 theta1 = -30 theta2 = 60 set angles degrees set style fill solid noborder set object circle at first 0,0 front size r2 arc [theta1:theta2] fillcolor lt 1 set object circle at first 0,0 front size r1 fillcolor rgb 'white' plot -10 notitle 

It is important here that the x and y axes have the same unit ( set size ratio -1 ), since the circle object is defined in units of the first x axis and does not take into account the y axis at all. If you have nothing else to build, you should use the plot command, which displays something outside of certain ranges. Without a graph, objects are not drawn.

Result from 4.6.5:

In the next version 5.0, you can use pseudo-data (with a special file name + ) along with the filledcurves build filledcurves :

 r1 = 0.5 r2 = 1.0 theta1 = 20 theta2 = 135 set polar set angles degrees set size ratio -1 unset raxis unset rtics set trange [theta1:theta2] set style fill solid noborder plot '+' using 1:(r1):(r2) with filledcurves notitle