Thank you, Messrs Barradas and Gross, for your very helpful advice. Philip
Message: 21
Date: Wed, 24 Mar 2021 22:41:25 -0400
From: "Avi Gross" <avigross at verizon.net>
To: <r-help at r-project.org>
Subject: Re: [R] Including a ggplot call with a conditional geom in a
function
Message-ID: <07e801d72120$59e5c720$0db15560$@verizon.net>
Content-Type: text/plain; charset="us-ascii"
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))
______________________________________________
Message: 24
Date: Thu, 25 Mar 2021 06:23:48 +0000
From: Rui Barradas <ruipbarradas at sapo.pt>
To: phil at philipsmith.ca, r-help at r-project.org
Subject: Re: [R] Including a ggplot call with a conditional geom in a
function
Message-ID: <a190f6cc-20b6-929b-8e7b-9a4ca7b0c717 at sapo.pt>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
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