CODEWITHSUNDEEP
rggplot2
Blue Magister
Blue Magister

Reputation: 13363

How do I convert this ggplot2 bar plot to a line plot?

I have a dataset with a discrete, ordered factor on the x-axis. I'd like to change the rendering from a bar graph to a line graph (in the style of geom_freqpoly). I can't use geom_freqpoly straight because I already have my data aggregated, and I don't know how to change the statistic from stat = "bin" to stat = "identity". How can I make this happen?

Here's the data:

temp <- structure(list(wday = structure(c(1L, 1L, 2L, 2L, 3L, 3L, 4L, 
4L, 5L, 5L, 6L, 6L, 7L, 7L), .Label = c("Monday", "Tuesday", 
"Wednesday", "Thursday", "Friday", "Saturday", "Sunday"), class = c("ordered", 
"factor")), splitter = c(FALSE, TRUE, FALSE, TRUE, FALSE, TRUE, 
FALSE, TRUE, FALSE, TRUE, FALSE, TRUE, FALSE, TRUE), N = c(250245, 
40845, 209685, 45946, 200983, 49403, 142869, 52212, 88589, 48175, 
51061, 25317, 84012, 7994), price1 = c(22.79, 70.20, 35.92, 87.66, 
48.98, 55.37, 22.56, 88.50, 26.12, 63.29, 35.88, 73.79, 33.12, 82.80
)), .Names = c("wday", "splitter", "N", "price1"), class = "data.frame", 
row.names = c(NA, -14L))

And here's the plot:

ggplot(melt(temp,id.vars = c("wday","splitter")), 
  aes(x = wday, y = value, fill = splitter)) + 
  geom_bar(stat = "identity", position = "dodge") + 
  facet_grid(variable ~ ., scale = "free_y")

Though I would think the following code would work, it does not:

ggplot(melt(temp,id.vars = c("wday","splitter")), 
  aes(x = wday, y = value, colour = splitter)) + 
  geom_point() + geom_line() +
  facet_grid(variable ~ ., scale = "free_y")

Upvotes: 3

Views: 2040

Answers (1)

Blue Magister
Blue Magister

Reputation: 13363

The issue was a missing group aesthetic. The function geom_line uses the factors as the default grouping variables (here, wday and splitter), and so each group is a single data point. Specifying the grouping in aes renders the lines as desired:

ggplot(melt(temp,id.vars = c("wday","splitter")), 
  aes(x = wday, y = value, colour = splitter, group = splitter)) + 
  geom_point() + geom_line() +
  facet_grid(variable ~ ., scale = "free_y")

Now with lines!

Upvotes: 3

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