Creating a function with column names and ggplot2

Question

I want to pass column names in a custom function that uses ggplot so I can recreate the graph.

The error states:

Error: All columns in a tibble must be 1d or 2d objects: * Column `x`

How can I update my function so I can define columns I want?

Thanks.

#DATA AND GRAPH
data("USArrests")
USArrests$IsHigh <- ifelse(USArrests[1] >= 13, 1 ,0)
ggplot(USArrests, aes(x=Assault, fill=factor(IsHigh)))+geom_density(alpha=0.25)+
geom_vline(aes(xintercept=mean(Assault[IsHigh==0],na.rm=T)),color="red",linetype="dashed",lwd=1)+
geom_vline(aes(xintercept=mean(Assault[IsHigh==1],na.rm=T)),color="blue",linetype="dashed",lwd=1)+
scale_x_continuous()+
  theme_classic()


##ATTEMPT AT FUNCITON
Test <- function(DATA, col1, col2){

ggplot(DATA, aes(x=col1, fill=factor(col2)))+
geom_density(alpha=0.25)+
geom_vline(aes(xintercept=mean(col1[col2==0],na.rm=T)),color="red",linetype="dashed",lwd=1)+
geom_vline(aes(xintercept=mean(col1[col2==1],na.rm=T)),color="blue",linetype="dashed",lwd=1)+
scale_x_continuous()+
  theme_classic()
}

#ERROR
Test(USArrests, "Assault", "IsHigh")

look at aes_string ggplot2.tidyverse.org/reference/aes_.html — ahly
– ahly, Commented Apr 16, 2019 at 19:54

Jilber Urbina · Accepted Answer · 2019-04-16 20:04:58Z

1

First of all, in your arguments you have col1 and in the function body you call col instead of col1, secondly you need to use get() for returning the value of a named object (col1 and col2). Try this...

Test <- function(DATA, col1, col2){
        ggplot(DATA, aes(x=get(col1), fill=factor(get(col2))))+
        geom_density(alpha=0.25)+
        geom_vline(aes(xintercept=mean(get(col1)[get(col2)==0],na.rm=T)),color="red",linetype="dashed",lwd=1)+
        geom_vline(aes(xintercept=mean(get(col1)[get(col2)==1],na.rm=T)),color="blue",linetype="dashed",lwd=1)+
        scale_x_continuous()+
        xlab(label = "Fixed Acidity Level")+
        ggtitle("Distribution of Fixed Acidity Levels")+
        theme_classic()
    }

Test(USArrests, "Assault", "IsHigh")

If you don't want to use get then...

Test <- function(DATA, col1, col2){

  col1 <- DATA[,col1] 
  col2 <- DATA[,col2]

  ggplot(DATA, aes(x=col1, fill=factor(col2)))+
    geom_density(alpha=0.25)+
    geom_vline(aes(xintercept=mean(col1[col2==0],na.rm=T)),color="red",linetype="dashed",lwd=1)+
    geom_vline(aes(xintercept=mean(col1[col2==1],na.rm=T)),color="blue",linetype="dashed",lwd=1)+
    scale_x_continuous()+
    xlab(label = "Fixed Acidity Level")+
    ggtitle("Distribution of Fixed Acidity Levels")+
    theme_classic()
}

edited Apr 16, 2019 at 20:04

answered Apr 16, 2019 at 19:57

Jilber Urbina

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1 Comment

Sean Mci Over a year ago

Thanks Jilber. Apologies I pasted in the wrong code (forgetting col1). I have edited it out. The second solution works perfectly. Thank you.

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