[R] barplot that displays sums of values of 2 y colums grouped by different variables

[kenneth dyson]

I am trying to create a barplot displaying the sums of 2 columns of data 
grouped by a variable. the data is set up like this:

"city" "n" "y" <br>
mon 100 200 <br>
tor 209 300 <br>
edm 98 87 <br>
mon 20 76 <br>
tor 50 96 <br>
edm 62 27 <br>

the resulting plot should have city as the x-axis, 2 bars per city, 1 
representing the sum of "n" in that city, the other the sum of "y" in 
that city.

If possible also show the sum in each bar as a label?

I aggregated the data into sums like this:

sum_data <- aggregate(. ~ City,data=raw_data,sum)

this gave me the sums per city as I wanted but for some reason 1 of the 
cities is missing in the output.

Using this code for the plot:

ggplot(sum_data,aes(x = City,y = n)) + geom_bar(aes(fill = y),stat = 
"identity",position = "dodge")

gave be a bar plot with one bar per city showing the sum of y as a color 
gradient. not what I expected given the "dodge" command in geom_bar.

Thanks.