void uvector (xfrom, yfrom, xto, yto, ltow, size, type)  ARROW.C Level 3
float xfrom, yfrom Starting point for the vector in user (plot) units.
float xto, yto End point for the vector in user units.
float ltow The ratio of the length of the arrowhead to its half-width.
float size The size of the head in inches (or cm) on a full-page output.
char *type
A 2-digit string mn describing the type and size of the arrowhead(s): 
= m is the form of the arrowhead(s) 
= n is the location of the arrowhead(s) 
= 0 none 
= 1 at (xto, yto
= 2 at both ends pointing outward




uvector() allows the user to label and dimension plots more easily and permits the drawing of vector fields. The arrow 
head is controlled by the two integers in the string type. All measurements are relative to a full-page output and are scaled with the size of the drawing page. uvector() uses the units of the plot axes.