passing parameters to ggplot

Question

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?

score 43 · Accepted Answer · answered Jun 27 '11 at 05:46

43

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?

answered Jun 27 '11 at 05:46

Grega Kešpret

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Beautiful. I simply didn't know this option existed. Thanks. – gappy Jun 27 '11 at 06:20
1

knew it, forgot it. rediscovered it thanks to your answer. +1 – Matt Bannert Nov 01 '12 at 15:06
Why does the DS not require "", but x and y does? Could you please explain. – Geekuna Matata May 14 '14 at 19:50
1

Great ! I haven't known option aes_string until I see this post. – BioCoder Sep 17 '15 at 07:47
Never knew about aes_string. Thanks for this. – minion Sep 19 '18 at 06:04

Triad sou. · Answer 2 · 2011-06-28T09:08:38.680

8

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.

edited Jun 28 '11 at 09:08

answered Jun 27 '11 at 06:13

Triad sou.

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A better approach would be to skip the conversion to text, and only build the aes component: `xName <- substitute(x); yName <- substitute(y); eval(substitute(aes(x, y), list(x = xName, y = yName)))` – hadley Jun 27 '11 at 12:58
Thank you @hadley. I think this approach is more simple than mine. – Triad sou. Jun 28 '11 at 05:16

score 1 · Answer 3 · answered Mar 30 '18 at 23:37

1

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 )

answered Mar 30 '18 at 23:37

ozgeneral

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Valentin_Ștefan · Answer 4 · 2019-01-10T18:24:47.473

1

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

edited Jan 10 '19 at 18:24

answered Jan 10 '19 at 16:47

Valentin_Ștefan

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Thanks. It helped me a lot! Can you explain the match.call argument ? – Luis Feb 06 '19 at 22:34
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Hi @Luis. Hadley Wickham wrote about some usages of `match.call()` in the section [Capturing the current call](http://adv-r.had.co.nz/Expressions.html#capturing-call) of his [Advanced R](http://adv-r.had.co.nz) book. Maybe that helps with more details. – Valentin_Ștefan Feb 08 '19 at 12:21

passing parameters to ggplot

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