Show percent % instead of counts in charts of categorical variables

Question

I'm plotting a categorical variable and instead of showing the counts for each category value. I'm looking for a way to get `ggplot` to display the percentage of values in that category. Of course, it is possible to create another variable with the calculated percentage and plot that one, but I have to do it several dozens of times and I hope to achieve that in one command. I was experimenting with something like ``` qplot(mydataf) + stat_bin(aes(n = nrow(mydataf), y = ..count../n)) + scale_y_continuous(formatter = "percent") ``` but I must be using it incorrectly, as I got errors. To easily reproduce the setup, here's a simplified example: ``` mydata <- c ("aa", "bb", NULL, "bb", "cc", "aa", "aa", "aa", "ee", NULL, "cc"); mydataf <- factor(mydata); qplot (mydataf); #this shows the count, I'm looking to see % displayed. ``` In the real case, I'll probably use `ggplot` instead of `qplot`, but the right way to use stat_bin still eludes me. I've also tried these four approaches: ``` ggpl…

Accepted Answer

Since this was answered there have been some meaningful changes to the `ggplot` syntax. Summing up the discussion in the comments above:

```
 require(ggplot2)
 require(scales)

p <- ggplot(mydataf, aes(x = foo)) +  
        geom_bar(aes(y = (..count..)/sum(..count..))) + 
        ## version 3.0.0
        scale_y_continuous(labels=percent)
```

Here's a reproducible example using `mtcars`:

```
 ggplot(mtcars, aes(x = factor(hp))) +  
        geom_bar(aes(y = (..count..)/sum(..count..))) + 
        scale_y_continuous(labels = percent) ## version 3.0.0
```

This question is currently the #1 hit on google for 'ggplot count vs percentage histogram' so hopefully this helps distill all the information currently housed in comments on the accepted answer.

Remark: If `hp` is not set as a factor, ggplot returns:

Show percent % instead of counts in charts of categorical variables

Solution

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