wbuchanan / stata-clipline

Stata implementation of Cohen-Sutherland line clipping algorithm. This is an intermediate program to help support clipping in various applications.

clipline

This package implements the Cohen-Sutherland line clipping algorithm in Stata. This is an intermediate program to help support clipping in various applications especially when dealing with spatial data.

Note: This is a beta release and still needs to be improved. It has been uploaded here for testing purposes only. Feedback is always welcome!

You can install the program as follows:

net install clipline, from("https://raw.githubusercontent.com/asjadnaqvi/stata-clipline/main/installation/") replace

and then check:

help clipline

for options. The required syntax is as follows:

clipline x1 y1 x2 y2, [box(x_low xhigh y_low y_high)] [offset(number)] [lines] [box]

Here is a test code, which is also provided in the dofile above:

clear
set obs 100


// generate random lines
gen id = _n
gen x1 = runiform(1,50)
gen y1 = runiform(1,50)
gen x2 = runiform(1,50)
gen y2 = runiform(1,50)

You can use a 10% extent (default) option to generate the line clippings:

clipline x1 y1 x2 y2, lines addbox

The option lines adds the information on the lines back to Stata. The option addbox adds the box bounds back to Stata. Both are specified for drawing the box:

	twoway ///
		(pcspike y1 x1 y2 x2, lw(thin) lc(gs12)) ///
		(pcspike clip_y1 clip_x1 clip_y2 clip_x2, lw(thin)) ///
		(line box_y box_x, lc(black) lw(thin)) ///
			, legend(off) 

You can also specify your own box and clipping extent:

clipline x1 y1 x2 y2, box(5 35 10 40) offset(-0.2) lines addbox

Here we define a custom box bounds and then reduce its size by 20%.

	twoway ///
		(pcspike y1 x1 y2 x2, lw(thin) lc(gs12)) ///
		(pcspike clip_y1 clip_x1 clip_y2 clip_x2, lw(thin)) ///
		(line box_y box_x, lc(black) lw(thin)) ///
			, legend(off)