ref: 85d0f0e1a2c05afee5a101c1e51a3ddd2ff2a5f6 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); }