There are two commands to multiply a matrix and a vector, `vectrans` and `coordtrans`. They assume the vector is in column
form and premultiply the matrix to the vector. If the vector contains
four numbers, the two commands are identical. If the vector has three
elements, a fourth is added; a 0 for `vectrans` and a 1 for `coordtrans`. The difference is that vectors are not affected by
translations during transformations, while coordinates are.

- (C++)
**vectrans**- Multiple the matrix m with the vector v (length 4); returns a vector*m v* **coordtrans**- Multiple the matrix m with the coordinate v (length 3); returns a vector*m v*

Examples: vmd > vectrans [transaxis z 90] {1 0 0} Info) -3.67321e-06 1.0 0.0 vmd > vectrans [transvecinv {-3 4 -12}] {-3 4 -12} Info) 13.0 -1.8e-05 5.8e-05

vmd@ks.uiuc.edu