The function draws vectors {ax, ay, az} along a curve {x, y, z}. The length of arrows are proportional to \sqrtax^2+ay^2+az^2. String pen specifies the color (see section Line styles). By default (pen="") color from palette is used (see section Pallete and colors). Parameter len set the vector length factor (if non-zero) or vector length to be proportional the distance between curve points (if len=0). The minor sizes of all arrays must be equal and large 2. The plots are drawn for each row if one of the data is the matrix. See also Vect. See section Traj sample, for sample code and picture.