Skip to content

Including a ggplot call with a conditional geom in a function

3 messages · phii m@iii@g oii phiiipsmith@c@, Avi Gross, Rui Barradas

Original
phii m@iii@g oii phiiipsmith@c@
# 
How can I write an R function that contains a call to ggplot within it, 
with one of the ggplot geom statements being conditional? In my reprex, 
I want the plot to contain a horizontal zero line if the y values are 
both positive and negative, and to exclude the horizontal line if all of 
the y values are of the same sign. I tried a simple if statement, but it 
does not work. Suggestions appreciated. Philip

library(rlang)
library(tidyverse)

a <- c(1:8)
b <- c(23,34,45,43,32,45,68,78)
c <- c(0.34,0.56,0.97,0.33,-0.23,-0.36,-0.11,0.17)
df <- data.frame(a,b,c)

posNeg <- function(x) {
   ifelse(sum(x>0)>0 & sum(x>0)<length(x), y <- TRUE,y <- FALSE)
}
plotLineFunc <- function(MYdf,MYx,MYy) {
     ggplot(MYdf,aes(x={{MYx}},y={{MYy}}))+
     #if(posNeg({{MYy}})) geom_hline(yintercept=0,size=0.2)+   # This 
does not work
     geom_line(colour="black",size=0.5)
}
(plot1 <- plotLineFunc(df,a,b))
(plot2 <- plotLineFunc(df,a,c))
Avi Gross
# 
This may not be the right place to ask about ggplot which is part of
packages but are you aware how ggplot works additively?

You can say something like:

P <- ggplot(...) ... + ...

Then later say:

P <- p + geom_...()

And so on.

So if you set al the layers you want first into a variable like p, then in
an if statement you selectively add in one or another layer and finally add
in all remaining layers before printing it, would that simply meet your
need?

Realistically, ggplot creates a data structure and the PLUS of other layers
updates or expands that structure but nothing happens till you print it and
it evaluates the data structure.

-----Original Message-----
From: R-help <r-help-bounces at r-project.org> On Behalf Of phil at philipsmith.ca
Sent: Wednesday, March 24, 2021 10:24 PM
To: r-help at r-project.org
Subject: [R] Including a ggplot call with a conditional geom in a function

How can I write an R function that contains a call to ggplot within it, with
one of the ggplot geom statements being conditional? In my reprex, I want
the plot to contain a horizontal zero line if the y values are both positive
and negative, and to exclude the horizontal line if all of the y values are
of the same sign. I tried a simple if statement, but it does not work.
Suggestions appreciated. Philip

library(rlang)
library(tidyverse)

a <- c(1:8)
b <- c(23,34,45,43,32,45,68,78)
c <- c(0.34,0.56,0.97,0.33,-0.23,-0.36,-0.11,0.17)
df <- data.frame(a,b,c)

posNeg <- function(x) {
   ifelse(sum(x>0)>0 & sum(x>0)<length(x), y <- TRUE,y <- FALSE) }
plotLineFunc <- function(MYdf,MYx,MYy) {
     ggplot(MYdf,aes(x={{MYx}},y={{MYy}}))+
     #if(posNeg({{MYy}})) geom_hline(yintercept=0,size=0.2)+   # This 
does not work
     geom_line(colour="black",size=0.5)
}
(plot1 <- plotLineFunc(df,a,b))
(plot2 <- plotLineFunc(df,a,c))

______________________________________________
R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Rui Barradas
# 
Hello,

In the following code, the fixed parts of the plot are drawn first, 
assigning the plot to p. Then geom_hline is conditionally added to p and 
the result returned to caller.
This may be a problem if the conditional geom needs to be in a specified 
order in the plot. Function plotLineFunc2 adds everything in the order 
of the question and is probably a better way of solving the problem.

I have also rewritten posNeg() without ifelse.

posNeg <- function(x) sum(x>0)>0 & sum(x>0)<length(x)

plotLineFunc <- function(MYdf,MYx,MYy) {
   p <- ggplot(MYdf,aes(x={{MYx}},y={{MYy}}))+
     geom_line(colour="black",size=0.5)
   if(posNeg({{MYy}}))
     p + geom_hline(yintercept=0,size=0.2)
   else p
}

plotLineFunc2 <- function(MYdf,MYx,MYy) {
   p <- ggplot(MYdf,aes(x={{MYx}},y={{MYy}}))
   p <- if(posNeg({{MYy}}))
     p + geom_hline(yintercept=0,size=0.2)
   else p
   p + geom_line(colour="black",size=0.5)
}


(plot1 <- plotLineFunc(df,a,b))
(plot2 <- plotLineFunc(df,a,c))


Hope this helps,

Rui Barradas

?s 02:24 de 25/03/21, phil at philipsmith.ca escreveu: