How to order bars in a bar graph using ggplot2

Question

I am trying to make a bar graph where the largest bar would be nearest to the y axis and the shortest bar would be furthest. 

So I have considered a table like this

    Name   Position
1   James  Goalkeeper
2   Frank  Goalkeeper
3   Jean   Defense
4   Steve  Defense
5   John   Defense
6   Tim    Striker

Here, I am trying to build a bar graph that would show the number of players according to the position

p <- ggplot(theTable, aes(x = Position)) + geom_bar(binwidth = 1)

But, the graph shows the goalkeeper bar first then the defense, and finally the striker one.

 I want the graph to be ordered so that the defense bar is closest to the y-axis, the goalkeeper one, and finally the striker one. 

Answer 1

The key to ordering is to set the levels of the factor in the order you want. 

An ordered factor is not required; the extra information in an ordered factor isn't necessary and if these data are being used in any statistical model, the wrong parametrization might result — polynomial contrasts aren't right for nominal data such as this.

## set the levels in order we want
theTable <- within(theTable, 
                   Position <- factor(Position, 
                                      levels=names(sort(table(Position), 
                                                        decreasing=TRUE))))
## plot
ggplot(theTable,aes(x=Position))+geom_bar(binwidth=1)

We simply need to set the factor levels to be in the desired order. There are multiple ways of doing this depending on the situation. For instance, we could do:

levels(theTable$Position) <- c(...)

and simply list the levels in the desired order on the right-hand side. You can also specify the level order within the call factor as above:

theTable$Position <- factor(theTable$Position, levels = c(...))