Return call from ggplot object

Question

I\'ve been using ggplot2 for a while now, and I can\'t find a way to get formula from ggplot object. Though I can get basic info with summary

Answer 1

You can store any R code as an expression with 'expression()' and then evaluate it with 'eval()'. e.g.

p <- expression(qplot(data = mtcars, x = factor(cyl), geom = "bar", fill = factor(cyl)) + 
     scale_fill_manual(name = "Cylinders", value = c("firebrick3", "gold2", "chartreuse3")) + 
     stat_bin(aes(label = ..count..), vjust = -0.2, geom = "text", position = "identity") + 
     xlab("# of cylinders") + ylab("Frequency") + 
     opts(title = "Barplot: # of cylinders"))

then

eval(p)

will produce the plot but the original code is still stored in the variable 'p' as an expression.

so

p

produces

expression(qplot(data = mtcars, x = factor(cyl), geom = "bar", 
    fill = factor(cyl)) + scale_fill_manual(name = "Cylinders", 
    value = c("firebrick3", "gold2", "chartreuse3")) + stat_bin(aes(label = ..count..), 
    vjust = -0.2, geom = "text", position = "identity") + xlab("# of cylinders") + 
    ylab("Frequency") + opts(title = "Barplot: # of cylinders"))

which is what we started with.

'eval()' can also evaluate a character string as an expression if parsed as text with parse(), e.g.

eval(parse(text='f(arg=value)')

Answer 2

It's not currently possible to go from a ggplot2 object to the code that (might have) created it.