title: Percentage sign binary operator in ggplot R
body: <p>I used percentage signs in the column names of a data frame. So far, I haven't encountered any disadvantages by doing so.</p>
  
  <p>Now I would like to create a ggplot with my data and get the following error due to the use of percentage signs:</p>
  
  <pre><code>Error in stat_boxplot(geom = "errorbar") + geom_boxplot() : 
  non-numeric argument to binary operator
  </code></pre>
  
  <p>Is there any way to still create a ggplot without having to remove the percentage sign in the column name?
  I tried putting the name in apostrophes, but this didn't help:</p>
  
  <pre><code>#'Values_in%'
  #`Values_in%`
  </code></pre>
  
  <p>Here is a test data frame:</p>
  
  <pre><code>test_data_frame &lt;- as.data.frame(rnorm(n=10, mean=5, sd=1))
  test_data_frame[,2] &lt;- sample(1:2, 10, replace = TRUE)
  colnames(test_data_frame) &lt;- c("Values", "Labels_assign") ## like this it works in ggplot
  colnames(test_data_frame) &lt;- c("Values_in%", "Labels_assign") ## this doesn't work in ggplot
  </code></pre>
  
  <p>And here is the code for the plot:</p>
  
  <pre><code>library(ggplot2)
  ggplot(test_data_frame, aes(x=factor(Labels_assign), y=Values_in%, fill=factor(Labels_assign)))  + 
    stat_boxplot(geom ='errorbar') + 
    geom_boxplot() +
    ggtitle("Box-Whisker-Plot") +
    xlab("X-Axis") +
    ylab("Y-Axis") +
    theme(plot.title = element_text(face="bold", size=16, hjust=0.5)) +
    theme(axis.title.x = element_text(face="bold", size=12)) +
    theme(axis.title.y = element_text(face="bold", size=12)) +
    theme(legend.title = element_text(face="bold")) +
    scale_fill_brewer(palette="Pastel2", name="Cluster")
  </code></pre>