Formatting dates on X axis in ggplot2

Question

I'm having a very, very tough time getting the x-axis to look correct for my graphs.

Here is my data:

df <- data.frame(
  Month = factor(c(
    "2011-07-31", "2011-08-31", "2011-09-30", "2011-10-31", "2011-11-30",
    "2011-12-31", "2012-01-31", "2012-02-29", "2012-03-31", "2012-04-30",
    "2012-05-31", "2012-06-30"
  )),
  AvgVisits = c(
    6.98655104580674, 7.66045407330464, 7.69761337479304, 7.54387561322994,
    7.24483848458728, 6.32001400498928, 6.66794871794872, 7.207780853854,
    7.60281201431308, 6.70113837397123, 6.57634103019538, 6.75321935568936
  )
)

Here is the chart I am trying to graph:

ggplot(df, aes(x = Month, y = AvgVisits)) + 
  geom_bar() +
  theme_bw() +
  labs(x = "Month", y = "Average Visits per User")

That chart works fine - but, if I want to adjust the formatting of the date, I believe I should add this: scale_x_date(labels = date_format("%m-%Y"))

I'm trying to make it so the date labels are 'MMM-YYYY'

ggplot(df, aes(x = Month, y = AvgVisits)) + 
  geom_bar() +
  theme_bw() +
  labs(x = "Month", y = "Average Visits per User") +
  scale_x_date(labels = date_format("%m-%Y"))

When I plot that, I continue to get this error:

stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.

Despite hours of research on formatting of geom_line and geom_bar, I can't fix it. Can anyone explain what I'm doing wrong?

Edit: As a follow-up thought: Can you use date as a factor, or should you use as.Date on a date column?

Have you loaded library(scales)?

smillig
– smillig

2012-07-31 20:31:31 +00:00
Commented Jul 31, 2012 at 20:31 — smillig
– smillig, Commented Jul 31, 2012 at 20:31
@smillig yes - scales is loaded.

mikebmassey
– mikebmassey

2012-07-31 20:32:36 +00:00
Commented Jul 31, 2012 at 20:32 — mikebmassey
– mikebmassey, Commented Jul 31, 2012 at 20:32

user5099519 · Accepted Answer · 2017-03-21 14:28:13Z

146

To show months as Jan 2017 Feb 2017 etc:

scale_x_date(date_breaks = "1 month", date_labels =  "%b %Y")

Angle the dates if they take up too much space:

theme(axis.text.x=element_text(angle=60, hjust=1))

answered Mar 21, 2017 at 14:28

user5099519

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8 Comments

Ufos Over a year ago

almost went crazy, trying to figure out why this wouldn't work. Figured out, theme_bw() overwrites anything theme() does. Reordered, and it works just fine. Leaving it here in case, someone is having the same issue.

cloudscomputes Over a year ago

Appreciate your answer, this helps me, write down my words to show my appreciation

AmphotericLewisAcid Over a year ago

This should definitely be the accepted answer to this question. The other one requires you to have the "Scales" library installed and loaded, whereas this one uses functionally that already exists in ggplot2.

Ufos Over a year ago

@stevec that is true for most programming languages. It's more important here that theme_bw() overwrites other theme() configurations, which could be confusing. It's only tangently related to this answer.

camille Over a year ago

@AmphotericLewisAcid ggplot2 imports scales, so if someone is using ggplot, they've already got scales installed

|

joran · Accepted Answer · 2016-02-29 16:49:46Z

91

Can you use date as a factor?

Yes, but you probably shouldn't.

...or should you use as.Date on a date column?

Yes.

Which leads us to this:

library(scales)
df$Month <- as.Date(df$Month)
ggplot(df, aes(x = Month, y = AvgVisits)) + 
  geom_bar(stat = "identity") +
  theme_bw() +
  labs(x = "Month", y = "Average Visits per User") +
  scale_x_date(labels = date_format("%m-%Y"))

enter image description here

in which I've added stat = "identity" to your geom_bar call.

In addition, the message about the binwidth wasn't an error. An error will actually say "Error" in it, and similarly a warning will always say "Warning" in it. Otherwise it's just a message.

edited Feb 29, 2016 at 16:49

answered Jul 31, 2012 at 20:51

joran

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6 Comments

mikebmassey Over a year ago

Spot on. Thanks. I hadn't seen stat = "identity" before. Going to research that more now. Thanks.

joran Over a year ago

@mikebmassey The basic thing to remember with stat = "identity" is that if you're doing bar plots and you've already aggregated the data so you have the heights of each bar already, then use it.

mikebmassey Over a year ago

Follow-up related to a line chart for this: so this is only applicable to bar plots - I just tried to plug the same thing with a geom_line - with and without stat = "identity" - I get this warning `geom_path: Each group consist of only one observation. If I only have 1 data group, why would I need to group to make it work? Thanks

Peyman Over a year ago

Error in date_format("%m-%Y") : could not find function "date_format"

Eric Krantz Over a year ago

@Peyman you need library(scales) for date_format

|

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