Order discrete x scale by frequency/value

Question

I am making a dodged bar chart using ggplot with discrete x scale, the x axis are now arranged in alphabetical order, but I need to rearrange it so that it is ordered by the

Answer 1

I realize this is old, but maybe this function I created is useful to someone out there:

order_axis<-function(data, axis, column)
{
  # for interactivity with ggplot2
  arguments <- as.list(match.call())
  col <- eval(arguments$column, data)
  ax <- eval(arguments$axis, data)

  # evaluated factors
  a<-reorder(with(data, ax), 
             with(data, col))

  #new_data
  df<-cbind.data.frame(data)
  # define new var
  within(df, 
         do.call("<-",list(paste0(as.character(arguments$axis),"_o"), a)))
}

Now, with this function you can interactively plot with ggplot2, like this:

ggplot(order_axis(df, AXIS_X, COLUMN_Y), 
       aes(x = AXIS_X_o, y = COLUMN_Y)) +
        geom_bar(stat = "identity")

As can be seen, the order_axis function creates another dataframe with a new column named the same but with a _oat the end. This new column has levels in ascending order, so ggplot2 automatically plots in that order.

This is somewhat limited (only works for character or factor and numeric combinations of columns and in ascending order) but I still find it very useful for plotting on the go.