Return call from ggplot object

Question

I have been using it ggplot2for a while and I cannot find a way to get the formula from the object ggplot. Although I can get basic information using summary(<ggplot_object>)to get the full formula, I usually combed up and down the file .Rhistory. And it gets frustrating when you experiment with new graphs, especially when the code gets a little long ... so searching through a history file is not a very convenient way to do this ... Is there a more efficient way to do this? Just an illustration:

p <- 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")

I can get some basic information with summary:

> summary(p)
data: mpg, cyl, disp, hp, drat, wt, qsec, vs, am, gear, carb [32x11]
mapping:  fill = factor(cyl), x = factor(cyl)
scales:   fill 
faceting: facet_grid(. ~ ., FALSE)
-----------------------------------
geom_bar:  
stat_bin:  
position_stack: (width = NULL, height = NULL)

mapping: label = ..count.. 
geom_text: vjust = -0.2 
stat_bin: width = 0.9, drop = TRUE, right = TRUE 
position_identity: (width = NULL, height = NULL)

, . , - ... , ggplot!

Answer 1

ggplot2 , (, ).

Answer 2

R- ()(), "eval()". .

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"))

eval(p)

, 'p' .

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"))

.

'eval()' , parse(), .

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