title: Show number of observation in each facet group ggplot2
body: <p>I have this ggplot code and i think so far it went well according to my expectation.</p>
  
  <pre><code>    bi_tr%&gt;%
    filter(!is.na(bi_tr$`13e Toilet type`)) %&gt;%
  
    ggplot(aes(x=`12 Income`,fill=`13e Toilet type`,na.rm = TRUE))+ #this fill comment goes to define legend
    geom_histogram(binwidth=50,color="black")+ #setting default color for aes in histogram
    facet_wrap(vars(fill=`13e Toilet type`),nrow=3)+ #make 1 column and 3 rows
    labs(x="Income (USD/month)",y="Frequency",title = "Income by Toilet Type")+ #make title of axis and title
    theme(legend.title=element_blank(),strip.text.x = element_blank())+ #strip text.x deletes the title in each group
    scale_fill_manual(values =c("blue","yellow","grey"))+#set fill color
    theme(legend.justification=c(1,.5), legend.position=c(1,.5))   #setting legend location
  </code></pre>
  
  <p>But I want to show my total data observation in each facet group, I have tried stat_summary with fun.data=give.n yet the result showed "object 'give.n' not found"</p>
  
  <p>Please help some newbie here... thanks a million</p>