Pyxplot 
Examples  Labelled ellipse 
Using the ellipse command to draw a labelled ellipse Here, an ellipse of moderate eccentricity e is drawn using Pyxplot's ellipse command, and then its important features are labelled. The semimajor axis a and semiminor axis b are both marked, as well as the semilatus rectum L. Scriptset multiplot ; set nodisplay a = 5.0 # Semimajor axis b = a*2/3 # Semiminor axis e = sqrt(1(b/a)**2) # Eccentricity slr = a*(1e**2) # Length of semilatus rectum fd = a*e # Distance of focus from center # Draw ellipse ellipse center 0,0 semiMajor a semiMinor b with lw 3 # Draw points at center and focus set texthalign center ; set textvalign top set fontsize 1.5 point at 0,0 label "Center" with pointsize 2 plw 2 point at fd,0 label "Focus" with pointsize 2 plw 2 # Draw arrows and dotted lines on ellipse arrow from 0,0 to 0,b with twohead lw 2 lt 3 # Semiminor axis arrow from 0,0 to a,0 with twohead lw 2 lt 3 # Semimajor axis arrow from fd,0 to fd,slr with tw lw 2 lt 3 # SLR arrow from 0,0 to fd,0 with twohead lw 2 lt 3 # Focus <> Center # Label ellipse set texthalign center ; set textvalign center text r'$ae$' at fd/2,0.3 text r'$a$' at a/2,+0.3 text r'$b$' at 0.3,b/2 set texthalign left ; set textvalign center text r'$L=a(1e^2)$' at 0.2fd,slr/2 # Display diagram set display ; refresh
