title: Figure caption scientific names + symbols in textGrob gtable
body: <p>First of all I would like to thank Sir Baptiste for helping me improve my R script by adding a caption at the bottom left the of the combined plots using gtable/textGrob as shown below:</p>
  
  <pre><code>library(grid)
  library(gridExtra)
  library(ggplot2)
  
  p1 &lt;- p2 &lt;- ggplot()
  
  g1 &lt;- ggplotGrob(p1)
  g2 &lt;- ggplotGrob(p2)
  
  g &lt;- rbind(g1, g2)
  caption &lt;- textGrob("Figure 1. This is a caption", hjust=0, x=0)
  g &lt;- gtable::gtable_add_rows(g, unit(2,"mm") + grobHeight(caption), -1)
  g &lt;- gtable::gtable_add_grob(g, caption, nrow(g), l = 4, r = ncol(g))
  grid.newpage()
  grid.draw(g)
  </code></pre>
  
  <p>However, I want to add two more things:</p>
  
  <p>(1) Insert a scientific name to the caption, which should be written in italics. 
   - For example, based on the caption mentioned above, I want to italize only the word "is" while the rest are in plain text.</p>
  
  <p>(2) I will also add symbols in the caption, e.g. point shapes=c(1,22); colours=c("black", "red"); fill=c("red", "black").</p>
  
  <p>How am I going to do these? I am a novice user of R program, hence your help is much appreciated. Thank you.</p>
  
  <p>UPDATE:</p>
  
  <p>I have already addressed query 1 with the help of @Docconcoct, @user20650 and @baptiste using this script:</p>
  
  <pre><code>library(grid)
  library(gridExtra)
  library(ggplot2)
  
  g1 &lt;- ggplotGrob(pl)
  g2 &lt;- ggplotGrob(pl1)
  
  g &lt;- rbind(g1, g2)
  caption &lt;- textGrob(expression(paste("Figure 1. This",  italic(" is"), " a caption")), hjust=0, x=0)
  g &lt;- gtable::gtable_add_rows(g, unit(2,"mm") + grobHeight(caption), -1)
  g &lt;- gtable::gtable_add_grob(g, caption, nrow(g), l = 4, r = ncol(g))
  grid.newpage()
  grid.draw(g)
  </code></pre>
  
  <p>For query 2,  as stated by Sir @baptiste, in my original email to him, I already have a legend on the combined plots. However, in the figure caption, I need to state what are those symbols in the legend mean, and some other details of the plot. Based on the example given by Sir baptiste, I need to include what supp means, as well as the symbols of OJ (dark circle) and VC (dark triangle) in the caption. </p>
  
  <p>Again, many thanks!</p>