How to Access the Data Frame That Has Been Passed to Ggplot()

How do I access the data frame that has been passed to ggplot()?

mtcars %>% {
  ggplot(., aes(mpg, hp)) + 
  labs(title = paste("N =", nrow(.))) + 
  geom_point()
}

Note that when wrapping the whole ggplot call in {...} curly braces, you must use the . dot pronoun for the data argument in ggplot(., ...). Then you can call back that object using the . pronoun anywhere in the call.

How to extract summary() to a data frame applicable for data visualization in ggplot()?

You can access the resulting list up to the level where the table for the plot is found and save it as a data.frame. You can check the structure of the list by using str.

summ_list <- summary(fit.aj,conf.int=FALSE,newdata=data.frame(age=50,sex="Male"),cause=1)
df<-as.data.frame(summ_list $table$`1`$`age=50, sex=Male`)

#The desired plot with ggplot
ggplot(df, aes(x=time)) +
  geom_line(aes(y=cuminc)) +
  geom_ribbon(aes(ymin = lower, 
                              ymax = upper))

ggplot2, how do you use access dataframe elements from within the function?

The trick here is to use aes_string instead of using aes. The former allows you to pass strings as aesthetics. This allows you to pass a variable containing the string of the aesthetic, e.g. 'wt' in case of plotting mtcars. You need to modify your code like this:

library(ggplot2)
test <- function(fdata, fx) {
  p <- ggplot(fdata, aes_string(x = fx, y = "mpg")) + geom_point()
  print(p)
}
test(mtcars, "wt")

Extract data from a ggplot

To get values actually plotted you can use function ggplot_build() where argument is your plot.

p <- ggplot(mtcars,aes(mpg))+geom_histogram()+
      facet_wrap(~cyl)+geom_vline(data=data.frame(x=c(20,30)),aes(xintercept=x))

pg <- ggplot_build(p)

This will make list and one of sublists is named data. This sublist contains dataframe with values used in plot, for example, for histrogramm it contains y values (the same as count). If you use facets then column PANEL shows in which facet values are used. If there are more than one geom_ in your plot then data will contains dataframes for each - in my example there is one dataframe for histogramm and another for vlines.

head(pg$data[[1]])
  y count         x ndensity ncount density PANEL group ymin ymax
1 0     0  9.791667        0      0       0     1     1    0    0
2 0     0 10.575000        0      0       0     1     1    0    0
3 0     0 11.358333        0      0       0     1     1    0    0
4 0     0 12.141667        0      0       0     1     1    0    0
5 0     0 12.925000        0      0       0     1     1    0    0
6 0     0 13.708333        0      0       0     1     1    0    0
      xmin     xmax
1  9.40000 10.18333
2 10.18333 10.96667
3 10.96667 11.75000
4 11.75000 12.53333
5 12.53333 13.31667
6 13.31667 14.10000

head(pg$data[[2]])
  xintercept PANEL group xend  x
1         20     1     1   20 20
2         30     1     1   30 30
3         20     2     2   20 20
4         30     2     2   30 30
5         20     3     3   20 20
6         30     3     3   30 30

Use Name of Data Frame Passed to Function as Plot Title

You have not given a minimal example to show the problem. The following works for me:

a <- expand.grid(x=1:3, y=1:2)
f <- function(df){qplot(x, y, data=a, main=deparse(substitute(df)))}
f(a)

Were you doing something else?

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