Including a ggplot call with a conditional geom in a function

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:

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.