\begin{Schunk}
\begin{Sinput}
 x0 <- c(-1, -4, 4.5)
 y0 <- c(-1, -4, -8)
 x1 <- c(2, -2, -3)
 y1 <- c(4, 4, 18)
 mylengths <- c(0.2, 0.3, 0.15)
 mycodes <- c(3, 2, 1)
 bdraw()
 arrows(x0 = x0, y0 = y0, x1 = x1, y1 = y1, length = mylengths, code = mycodes)
\end{Sinput}
\end{Schunk}
