Function input used as string

Question

saving_ggplot <- function(name = 'default', plotname = last_plot()) {
  image_name = paste(name, ".png", sep="")
  ggsave(image_name, plot = plotname,
         scale = 1, 
         dpi = 300, limitsize = TRUE)
}

This is my function which saves a ggplot. However, I for the life of me cannot figure out how to take the name argument as a string.

for example if someone runes saving_ggplot(FILENAME, PLOTNAME)

it will just say no object FILENAME. In python I can just capture it and use it as str(), but using as.character or toString in R still doesn't work.

Error:

saving_ggplot(weightvsageTEST, weightvsageplot)
Error in paste(name, ".png", sep = "") : 
  object 'weightvsageTEST' not found

Successful call using ggsave:

ggsave('weightvsage.png', plot = last_plot(),
       scale = 1, 
       dpi = 300, limitsize = TRUE)

Can you include the actual code which tries to call saving_ggplot with FILENAME as a parameter? — Tim Biegeleisen
– Tim Biegeleisen, Commented May 26, 2018 at 14:42
Not 100% sure what you mean, included the error message for example. — Alexis Drakopoulos
– Alexis Drakopoulos, Commented May 26, 2018 at 14:43
Perhaps you are missing the point of my question. Is weightvsageTEST even defined somewhere? — Tim Biegeleisen
– Tim Biegeleisen, Commented May 26, 2018 at 14:45
no that's the point, I'm trying to use the input argument as a string and I don't know how to do that. I want to take whatever the user types in, for example weightvsageTEST and convert that to a string for the filename that gets created. — Alexis Drakopoulos
– Alexis Drakopoulos, Commented May 26, 2018 at 14:46

andrew_reece · Accepted Answer · 2018-05-26 16:32:31Z

2

You can use substitute():

saving_ggplot <- function(name, plotname) {
  image_name = paste0(substitute(name), ".png") # paste0 removes need for sep arg
  ggsave(image_name, plot = plotname,
         scale = 1, 
         dpi = 300, limitsize = TRUE)
}

saving_ggplot(foo, p) # saves foo.png

Alternately, if you want to stay within tidyverse quasiquotation syntax, use enexpr() instead:

enexpr(name) # instead of substitute(name)

Data:

N <- 100
df <- data.frame(x=rnorm(n=N), y=rnorm(n=N))
p <- ggplot(df, aes(x,y)) + geom_smooth()

answered May 26, 2018 at 16:32

andrew_reece

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