CODEWITHSUNDEEP
graphicsr
csgillespie
csgillespie

Reputation: 60492

How can I determine if a function generates a graph

Is there a way to determine if a function generates a figure in R?

For example, if we have functions f and g

f = function(x,y){plot(x,y)}
g = function(x,y){mean(x*y)}

I would like able to run 

createFigure(f(x,y))#Returns TRUE
createFigure(g(x,y))#Returns FALSE

Thanks

Upvotes: 7

Views: 269

Answers (2)

hadley
hadley

Reputation: 103938

makes_plot <- function(x) {
  before <- .Internal(getSnapshot())
  force(x)
  after <- .Internal(getSnapshot())
  !identical(before, after)
}

makes_plot(mean(1:10))
makes_plot(plot(1:10))

The .getSnapshot function was discovered by looking at the source of recordPlot().

Upvotes: 20

John
John

Reputation: 23758

If, for your purposes, it's OK to have all devices off before hand then checking .Devices would be fine because then plotting commands do make a new device. But then lines(), and points() would be exceptions.

In fact, this suggests that the question doesn't just have a true or false answer but depends on conditions. Some functions will draw something even if there is no open device while others will draw something if there is something else drawn. What would you want to do in that case?

Upvotes: 0

Related Questions