Plotting two different time series in R?

Question

I'm trying to plot two different time series on the same plot using the ggplot2 package in R. I'm not sure why it isn't working. I believe it may be because one of the series is daily data and one is monthly.

I wrote some code for two data frames:

ras <- data.frame(
  date=seq(as.Date("2004-10-01"), as.Date("2015-09-02"), by = "day"),
  CONSUMERS=runif(3989,80,120)
)

umich <- data.frame(
  observation_date=seq(as.Date("2004-10-01"), as.Date("2015-02-01"), by = "month"),
  UMCSENT=runif(125,80,100)
)

So I want both of them on the same ggplot. Suppose I try the following:

a <- ggplot() + 
  geom_line(data=umich,aes(observation_date,UMCSENT)) +
  geom_line(data=ras,aes(x=date,y=CONSUMERS))
a

I end up with this error:

Error: Invalid input: time_trans works with objects of class POSIXct only

I thought I could possibly add in argument like this but I get the same error:

a <- ggplot() + 
  geom_line(data=umich,aes(observation_date,UMCSENT)) +
  geom_line(data=ras,aes(x=date,y=CONSUMERS)) +
  scale_x_date(format = "%b-%Y")
a

To summarize, I'm trying to plot monthly and daily time series data on the same ggplot.

Answer 1

Not sure where the problem is. Using your data, here is what I get.

library(ggplot2)
library(scales)

ras <- data.frame(
  date=seq(as.Date("2004-10-01"), as.Date("2015-09-02"), by = "day"),
  CONSUMERS=runif(3989,80,120)
)

umich <- data.frame(
  observation_date=seq(as.Date("2004-10-01"), as.Date("2015-02-01"), by = "month"),
  UMCSENT=runif(125,80,100)
)

a <- ggplot() +
  geom_line(data=ras,aes(x=date,y=CONSUMERS)) +
  geom_line(data=umich,aes(observation_date,UMCSENT), color="red") +
  scale_x_date(labels=date_format('%b-%Y'))
a