ref: 3a4a6d2dd2a3dc812ad31a2c1ee663a7e7ed0bfa dir: /sys/src/cmd/plot/libplot/rvec.c/
#include "mplot.h" void rvec(double xx, double yy){ e1->copyx += xx; e1->copyy += yy; vec(e1->copyx, e1->copyy); }