|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.|
|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.