To get (xlo,xhi,ylo,yhi,zlo,zhi):
[min(x) max(x) min(y) max(y) min(z) max(z)] ;
As you have (x,y,z) data, select any two points in random and plot line. You may select random point using randsample or randperm. Once you get two points, you can get length using norm. Or by calculating the distance between them.