title: R - split legend in two columns
body: <p>I have the following R plot.</p>
  
  <pre><code>library(tidyverse)
  
  dat &lt;- data.frame(
    FunctionClass = factor(c("A", "B", "C", "D", "E", "F", "G", "H", "I",     "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "Y", "Z"), levels=c("A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "Y", "Z")),
    legend = c("A: RNA processing and modification", "B: Chromatin structure and dynamics", "C: Energy production and conversion", "D: Cell cycle control, cell division, chromosome partitioning", "E: Amino acid transport and metabolism", "F: Nucleotide transport and metabolism", "G: Carbohydrate transport and metabolism", "H: Coenzyme transport and metabolism", "I: Lipid transport and metabolism", "J: Translation, ribosomal structure and biogenesis", "K: Transcription", "L: Replication, recombination and repair", "M: Cell wall/membrane/envelope biogenesis", "N: Cell motility", "O: Posttranslational modification, protein turnover, chaperones", "P: Inorganic ion transport and metabolism", "Q: Secondary metabolites biosynthesis, transport and catabolism", "R: General function prediction only", "S: Function unknown", "T: Signal transduction mechanisms", "U: Intracellular trafficking, secretion, and vesicular transport", "V: Defense mechanisms", "W: Extracellular structures", "Y: Nuclear structure", "Z: Cytoskeleton"),
    Frequency=c(360,391,897,1558,1168,448,1030,536,732,1292,2221,2098,789,117,1744,732,437,5162,1251,2191,603,216,2,14,739)
  )
  
  dat &lt;- cbind(
    dat
    , Frequency2=c(523,900,400,155,168,428,1050,516,742,129,221,2698,7829,1147,144,7132,4437,562,1551,2691,103,516,22,12,939))
  
  p &lt;- dat %&gt;%
    gather("variable", "value", -FunctionClass, -legend) %&gt;%
    ggplot(aes(FunctionClass, value, fill = legend, group = variable)) +
    geom_bar(stat="identity", position=position_dodge(), colour="seashell") +
    guides (fill = guide_legend(ncol = 1)) +
    xlab("COG Class")
  
  p + theme(legend.position="bottom")
  </code></pre>
  
  <p>However, due to the quantity of legends in the plot, the legends take up a lot of space. Is there a way to split the legends into two columns, instead of one long column?</p>
  
  <p>Thanks!</p>