Unable to Pass Arguments in User Define Function t

I want to create a user define function that wraps around some popular ggplot code I found. I am getting the following error:

"Error in `[.data.frame`(DS, , xvar) : object 'xcol' not found"

The following is a small pseudo dataset to illustrate the issue.

n=25
dataTest <- data.frame(xcol=sample(1:3, n, replace=TRUE), ycol = rnorm(n, 5, 2), Cat=letters[1:5])

The user defined code is as here:

  TRIPLOT <- function (DS,xvar,yvar,zvar) {
 #localenv<-environment()
  gg <- data.frame(x=DS[,xvar],y=DS[,yvar],fill=DS[,zvar])
  empty<-ggplot()+geom_point(aes(1,1),colour="white") + theme( 
    plot.background = element_blank(),
    panel.background = element_blank(),
    panel.grid.minor = element_blank(),
    panel.border = element_blank(),
    panel.background = element_blank(),
    axis.title.x = element_blank(),
    axis.title.y = element_blank(),
    axis.text.x = element_blank(),
    axis.text.y = element_blank(),
    axis.ticks = element_blank())
  scatter <-ggplot(gg, aes_string(x=xvar,y=yvar), environment=environment())+
    geom_point(aes_string(color=zvar))+
    scale_color_manual(values=c("orange","purple"))+
    theme(legend.position=c(1,1), legend.justification=c(1,1))
  plot_top <- ggplot(gg,aes_string(x=xvar, fill=zvar), environment=environment())+geom_density(alpha=.5)+scale_fill_manual(values=c("orange","purple"))+theme(legend.position="none")
  plot_right <- ggplot(gg, aes_string(yvar, fill=zvar),environment=environment())+geom_density(alpha=.5)+coord_flip()+ scale_fill_manual(values=c("orange","purple"))+
    theme(legend.position="none", axis.title.x=element_blank())
  PLT <- grid.arrange(plot_top,empty,scatter,plot_right, ncol=2,nrow=2,widths=c(4,1), heights=c(1,4))
  print(PLT)
}

The function I am trying to run is the following:

TRIPLOT(dataTest,"xcol","ycol","Cat")

I added environment argument and the data.frame() argument as recommend by the post. I have also passed the arguments to the function in quotes. Thank you for any help.

Either pass the variable names as strings to the function, rename the variables in gg data frame; then use aes in place of aes_string; and use the gg data frame and its variable names in the calls to ggplot.

Or pass the variable names as strings to the function; then use aes_string (and skip the gg data frame).

In addition there is a problem with the number of colours in scale_fill_manual. I've commented those lines out.

library(gridExtra)
library(ggplot2)

n=25
dataTest = data.frame(
   xcol=sample(1:3, n, replace=TRUE), 
   ycol = rnorm(n, 5, 2), 
   Cat=letters[1:5])

EITHER:

 TRIPLOT <- function (DS,xvar,yvar,zvar) {
 #localenv<-environment()
  gg <- data.frame(x = DS[,xvar], y = DS[, yvar],fill = DS[,zvar])
  empty<-ggplot()+geom_point(aes(1,1),colour="white") + theme( 
    plot.background = element_blank(),
    panel.background = element_blank(),
    panel.grid.minor = element_blank(),
    panel.border = element_blank(),
    panel.background = element_blank(),
    axis.title.x = element_blank(),
    axis.title.y = element_blank(),
    axis.text.x = element_blank(),
    axis.text.y = element_blank(),
    axis.ticks = element_blank())

  scatter <-ggplot(gg, aes(x = x,y = y))+
    geom_point(aes(color = fill))+
    #scale_color_manual(values=c("orange","purple"))+
    theme(legend.position=c(1,1), legend.justification=c(1,1))

  plot_top <-ggplot(gg,aes(x = x, fill = fill))+
   geom_density(alpha=.5)+
   #scale_fill_manual(values=c("orange","purple"))+
    theme(legend.position="none")

  plot_right <-ggplot(gg, aes(x = y, fill = fill))+
       geom_density(alpha=.5)+coord_flip()+ 
       #scale_fill_manual(values=c("orange","purple"))+
    theme(legend.position="none", axis.title.x=element_blank())

  PLT<-grid.arrange(plot_top,empty,scatter,plot_right, ncol=2,nrow=2,widths=c(4,1), heights=c(1,4))
  print(PLT)
}

TRIPLOT(dataTest,"xcol","ycol","Cat")

OR:

 TRIPLOT <- function (DS,xvar,yvar,zvar) {
 #localenv<-environment()
  #gg <- data.frame(x = DS[,xvar], y = DS[, yvar],fill = DS[,zvar])
  empty<-ggplot()+geom_point(aes(1,1),colour="white") + theme( 
    plot.background = element_blank(),
    panel.background = element_blank(),
    panel.grid.minor = element_blank(),
    panel.border = element_blank(),
    panel.background = element_blank(),
    axis.title.x = element_blank(),
    axis.title.y = element_blank(),
    axis.text.x = element_blank(),
    axis.text.y = element_blank(),
    axis.ticks = element_blank())

  scatter <-ggplot(DS, aes_string(x = xvar,y = yvar))+
    geom_point(aes_string(color = zvar))+
    #scale_color_manual(values=c("orange","purple"))+
    theme(legend.position=c(1,1), legend.justification=c(1,1))

  plot_top <-ggplot(DS,aes_string(x = xvar, fill = zvar))+
   geom_density(alpha=.5)+
   #scale_fill_manual(values=c("orange","purple"))+
    theme(legend.position="none")

  plot_right <-ggplot(DS, aes_string(x = yvar, fill = zvar))+
       geom_density(alpha=.5)+coord_flip()+ 
       #scale_fill_manual(values=c("orange","purple"))+
    theme(legend.position="none", axis.title.x=element_blank())

  PLT<-grid.arrange(plot_top,empty,scatter,plot_right, ncol=2,nrow=2,widths=c(4,1), heights=c(1,4))
  print(PLT)
}

TRIPLOT(dataTest,"xcol","ycol","Cat")