[Maxima-discuss] explit plotting in wxdraw2d

[Evan C. <eva...@gm...>]

For a variety of reasons, I need to be able to plot a vertical line, wrt 
to the horizontal axis, in a plot. For the life of me, I'm not sure how 
to do this using wxdraw2d (or if its even possible). Suppose I want a 
simply x-y plot, with a horizontal line at y=200 over all x, and a 
vertical line at x=100 over all y.

First, I call a few things, and set some defaults:

load("draw")$

set_draw_defaults(
       grid=true,
       xaxis = true, yaxis = true,
         xaxis_type = solid, yaxis_type = solid,
       proportional_axes=xy)$

wxplot_size: [250, 250] $

wxdraw2d(x_voxel = 100,
    y_voxel = 100,
    line_width=2,color="black",
    explicit(200,x,0,250), /* horizontal line */
    explicit(100,y,0,250)); /* vertical */;


But, this doesn't work. It seems that explicit within wxdraw2d must be a 
function in x.If thats the case, then how the heck would you ever draw 
something like...x=100 over all y? In other words, a vertical reference 
line? The only way I could 'get something to work' seems like a kludge 
-- using polygon:

wxdraw2d(
    line_width=2,color="black",
    explicit(200,x,0,250), /* horizontal line */
    polygon([100,100],[0,250])); /* vertical */;

Does the trick but...is there a better way that I'm missing?

Thanks!