do.call in a function - object not found error

Question

I was trying to make my own function that will plot many plots side by side using ggplot and taking a list of dataframes as an argument. However, I run across this error, which as far as I have determined is related to do.call function and environment issues:

my_df<-data.frame(a=rnorm(25),b=runif(25))
my_list<-list(my_df,my_df*2)
reproducible_function<-function(a_list){
  dd<-list()
  for (i in 1:length(a_list)){
    p<-ggplot(data=a_list[[i]],aes(x=1:nrow(a_list[[i]]),y="something"))
    dd[[i]]<-p+geom_line(aes(y=a,colour="a"))+geom_line(aes(y=b,color="b"))
  }

  do.call(grid.arrange,dd)
}
reproducible_function(my_list)

however, I get the following error:

Error in nrow(a_list[[i]]) : object 'a_list' not found

When not in a function, everything runs smoothly. But when I try to use a do.call function inside my own function something happens (I get same kind of errors when using eval(parse)).

See https://stackoverflow.com/questions/22287498/scoping-of-variables-in-aes-inside-a-function-in-ggplot. You can solve the problem by adding `p$plot_env — bgoldst, Dec 27 '15 at 20:23
There is a similar solution at http://stackoverflow.com/questions/10659133/local-variables-within-aes. I tried this on your code and it worked. — steveb, Dec 27 '15 at 20:31
A workaround would be to add the `x` variable to the data frame: `a_list[[i]]$x — G. Grothendieck, Dec 27 '15 at 23:51

score 2 · Accepted Answer · answered Dec 27 '15 at 23:18

2

Just add this line right after you create p inside loop:

p$plot_env <- environment()

answered Dec 27 '15 at 23:18

Mirek Długosz

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do.call in a function - object not found error

1 Answers1