The USERSYM procedure is used to define the plotting symbol that marks points when the plotting symbol is set to plus or minus 8. Symbols can be drawn with vectors or can be filled. Symbols can be of any size and can have up to 50 vertices. See Defining Your Own Plotting Symbols .
The X and/or Y parameters define the vertices of the symbol as offsets from the data point in units of approximately the size of a character. In the case of a vector drawn symbol, the symbol is formed by connecting the vertices in order. If only one argument is specified, it must be a (2, N ) array of vertices, with element [0, i ] containing the X coordinate of the vertex, and element [1, i ] containing the Y. If both arguments are provided, X contains only the X coordinates.