title: How do you make ggplot labels use both labels = abs and labels=comma?
body: <p>I'm creating a population pyramid. I would like my axis to use absolute values so that I don't have negative numbers for population count. I would also like to have the tick marks on the x-axis formatted with commas so that instead of 30000 it would read 30,000. </p>
  
  <p>I know <code>labels=comma</code> will provide numbers that uses comma and I know that <code>labels =abs</code> will provide numbers that are in absolute values. 
  How do I combine the two options?</p>
  
  <pre><code>  #test data
     mfrawcensus &lt;- data.frame(Age = factor(rep(x = 1:90, times = 2)), 
                Sex = rep(x = c("Females", "Males"), each = 90),
                Population = sample(x = 1:60000, size = 180))
  
   censuspop &lt;-   ggplot(data=mfrawcensus,aes(x=Age,y=Population, fill=Sex)) + 
   geom_bar(data= subset(mfrawcensus,Sex=="Females"), stat="identity") + 
   geom_bar(data= subset(mfrawcensus,Sex=="Males"),
         mapping=aes(y=-Population),
         stat="identity",
         position="identity") + 
  scale_y_continuous(labels=comma) + 
  xlab("Age (years)")+ ylab("Population") + 
  scale_x_discrete(breaks =seq(0,90,5), drop=FALSE)+   coord_flip(ylim=c(-55000,55000))
  </code></pre>
  
  <p>I tried adding like another scale on top of the original one  to get absolute values but it didn't work. Here's my attempt:</p>
  
  <pre><code>   censuspyramid&lt;-censuspop+theme_bw() +theme(legend.position="none")
    + ggtitle("a")+scale_y_continuous(labels=abs)
  </code></pre>