title: Knitr kable/pandoc/pander/geom_title/grid.table custom cell formatting
body: <p>I would like to add symbols and letters before and after some numbers when using <code>knitr</code>'s <code>kable</code> function, but do not know how to do this efficiently. I am however also willing to consider <code>pandoc</code>/<code>pander</code> if its is better/more efficient.</p>
  
  <p>The end result should be an HTML table...or very good graphic of one....</p>
  
  <p>Please see the following code as a mock reproducible example that is in a .Rmd file:</p>
  
  <pre><code>### Notional and Cumulative P&amp;L
  
  ```{r echo=FALSE}
  Notional &lt;- 10000
  yday_pnl &lt;- -2942
  wtd_pnl &lt;- 2300
  mtd_pnl &lt;- -3334
  ytd_pnl &lt;- 5024
  
  yday_rtn &lt;- (yday_pnl/Notional)*10000
  wtd_rtn &lt;- (wtd_pnl/Notional)*10000
  mtd_rtn &lt;- (mtd_pnl/Notional)*10000
  ytd_rtn &lt;- (ytd_pnl/Notional)*10000
  
  Value &lt;- c(Notional,yday_pnl,wtd_pnl,mtd_pnl,ytd_pnl)
  rtn &lt;- c(NA,yday_rtn,wtd_rtn,mtd_rtn,ytd_rtn)
  
  COB.basics &lt;- as.data.frame(cbind(Value,rtn))
  rownames(COB.basics) &lt;- c('Notional','yday pnl','wtd_pnl','mtd_pnl','ytd_pnl')
  ```
  
  ```{r results='asis',echo=FALSE}
  kable(COB.basics,digits=2)
  ```
  </code></pre>
  
  <p>So similar to Excel's format type of currency or accountancy I would like the value field to have the $ sign for the <code>Value</code> column, and for the <code>rtn</code> column I would like to have the string <code>bps</code> after the numbers...also for readability purposes is it possible to have commas after three digits if it is before the decimal point? i.e. to represent thousands etc.</p>
  
  <p>Also is it possible to colour the cells? and also colour the text/numbers too? i.e. red for negative values?</p>