ref: 2ae2e5f856f8f95f8d780f9ffe0a0ebb634ffb1a 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); }