ggplot colour bar label date formatting

Question

Is it possible to format the number labels on a guide_colourbar to a date format e.g. %b %Y? So instead of having 17400 17700 18000 18300 on the Closing Date legend, there would be the %b %Y equivalents.

Example plot

Code used to produce the plot

Area = c(1705, 902, 1496, 1257, 763)
ClosePrice = c(2292500, 977520, 1990680, 1720840, 855330)
HasTerrace = c(FALSE, FALSE, TRUE, FALSE, TRUE)
CloseDate = as.Date(c('2017-03-17', '2017-02-28', '2018-05-09', '2020-03-01',
                      '2017-01-09'))
data <- data.frame(Area, ClosePrice, HasTerrace, CloseDate)

data %>%
  ggplot(aes(x=Area, y=ClosePrice, shape=HasTerrace)) +
  geom_point(aes(colour=CloseDate), size=3, alpha=0.8) +
  scale_color_viridis() +
  theme_minimal() +
  scale_x_continuous(expression(Indoor~Area~(ft^2)),
                     labels=label_comma()) +
  scale_y_continuous('Closing Price ($m)',
                     labels=label_number(accuracy=0.01, scale=10^-6)) +
  theme(legend.position='bottom', legend.box='vertical') +
  guides(shape = guide_legend(title='Has a Terrace'),
         colour = guide_colourbar(title='Closing Date',
                                  barwidth=10,
                                  labels=label_date(format='%b %Y')))

Answer 1

Here is a solution. The guide_colorbar() function does not accept the labels argument, so it ignores it. You need to add your labels to scale_color_viridis. However, that will create an error unless you also include trans = "date".

data %>%
  ggplot(aes(x=Area, y=ClosePrice, shape=HasTerrace)) +
  geom_point(aes(colour=CloseDate), size=3, alpha=0.8) +
  scale_color_viridis(name='Closing Date', 
                      trans = "date", 
                      labels = label_date(format = "%b %Y") )+
  theme_minimal() +
  scale_x_continuous(expression(Indoor~Area~(ft^2)),
                     labels=label_comma()) +
  scale_y_continuous('Closing Price ($m)',
                     labels=label_number(accuracy=0.01, scale=10^-6)) +
  theme(legend.position='bottom', legend.box='vertical') +
  guides(shape = guide_legend(title='Has a Terrace'),
         colour = guide_colourbar(barwidth=10))