CODEWITHSUNDEEP
rggplot2
gappy
gappy

Reputation: 10243

passing parameters to ggplot

would like to create a function that generates graphs using ggplot. For the sake of simplicity, the typical graph may be

ggplot(car, aes(x=speed, y=dist)) + geom_point()

The function I would like to create is of the type

f <- function(DS, x, y) ggplot(DS, aes(x=x, y=y)) + geom_point()

This however won't work, since x and y are not strings. This problem has been noted in previous SO questions (e.g., this one), but without providing, in my view, a satisfactory answer. How would one modify the function above to make it work with arbitrary data frames?

Upvotes: 21

Views: 13030

Answers (4)

Valentin_Ștefan
Valentin_Ștefan

Reputation: 6416

One approach that I can think of is using match.call() to reach the variable names contained by the parameters/arguments passed to the custom plotting function and then use eval() on them. In this way you avoid passing them as quoted to your custom function, if you do not like that.

library(ggplot2)

fun <- function(df, x, y) {
    arg <- match.call()
    ggplot(df, aes(x = eval(arg$x), y = eval(arg$y))) + geom_point()
} 
fun(mpg, cty, hwy) # no need to pass the variables (column names) as quoted / as strings

enter image description here

Upvotes: 1

ozgeneral
ozgeneral

Reputation: 6779

Another option is to use do.call. Here is a one line copy paste from a working code:

gg <- gg + geom_rect( do.call(aes, args=list(xmin=xValues-0.5, xmax=xValues+0.5, ymin=yValues, ymax=rep(Inf, length(yValues))) ), alpha=0.2, fill=colors )

Upvotes: 1

Triad sou.
Triad sou.

Reputation: 2971

I think it's possible the following type of codes, which only build the aes component.

require(ggplot2)

DS <- data.frame(speed=rnorm(10), dist=rnorm(10))

f <- function(DS, x, y, geom, opts=NULL) {
  aes <- eval(substitute(aes(x, y),
    list(x = substitute(x), y = substitute(y))))
  p <- ggplot(DS, aes) + geom + opts
}

p <- f(DS, speed, dist, geom_point())
p

However, it seems to be complicated approach.

Upvotes: 8

Grega Kešpret
Grega Kešpret

Reputation: 12107

One solution would be to pass x and y as string names of columns in data frame DS.

f <- function(DS, x, y) {    
  ggplot(DS, aes_string(x = x, y = y)) + geom_point()  
}

And then call the function as:

f(cars, "speed", "dist")

However, it seems that you don't want that? Can you provide an example why you would need different functionality? Is it because you don't want to have the arguments in the same data frame?

Upvotes: 42

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