Help deeded: Does a R graphical function return something special?
On 10/19/07, HU,ZHENGJUN <hhu at ufl.edu> wrote:
Hi All, When I tried to catch a returned value from a R graphical function or command (e.g., plot, lines, points, abline, title, xyplot, etc.), I always get a NULL value if it is executed correctly. For example: x <- c(1,2,3,4,5,9,13,19,36) plot.Comm <- plot(x) # plot.Comm <- try(eval(plot(x))) then plot.Comm has a NULL value. Obviously, this is not a good way to check if or not it is a graphical function or command since plot.Comm <- NULL also lets plot.Comm be NULL. Does anyone knows: (1) that a R graphical function or command (e.g., plot, lines, points, abline, title, xyplot, etc.) could return something special if it is run correctly, which is different from those returned from executing any R non-graphical functions or commands? (2) that there is an easy way for a R programmer to know that a R function or command is a graphical one before executing it?
You should always consult the appropriate help page. ?lines mentions no return value (and returns NULL), but ?hist and ?xyplot do describe non-trivial return values. -Deepayan