I have two points:
\coordinate (A) at (1,2); \coordinate (B) at (13.2,-23.4);
I would like to draw a vector pointing from point A to point B. The vector starts from point A, its length is other specified, and its end is not at point B. See the figure below. Is there an automatic way to draw the arrow such that I need not to calculate the coordinate of the end of the arrow every time?