ref: 2d4a2c5c2065a32b6b5bd6a0e887af1574a8dfec
dir: /sys/src/cmd/plot/libplot/range.c/
#include "mplot.h"
void range(double x0, double y0, double x1, double y1){
e1->xmin = x0;
e1->ymin = y0;
e1->scalex = e1->sidex / (x1 - x0 );
e1->scaley = e1->sidey / (y1 - y0 );
e1->quantum=e0->quantum/sqrt(e1->scalex*e1->scalex +
e1->scaley*e1->scaley);
if(e1->quantum < .01)
e1->quantum = .01;
}