Monthly time series plot with years on x-axis in R

Question

I'd really appreciate any help to create a time series plot in R. I'm a total newbie and my programming knowledge is really limited. I just need to create this one graph and it has to be done in R, not Excel.

I have the following monthly data:

Time   HML
200207 6.28 
200208 3.44
200209 8.03
...
201412 1.47

I have a really hard time to understand how time variable is defined or how it should be converted.

Now I need to plot it so on the X-axis there are only years visible i.e. 2002, 2003, 2004, (...), 2014.

Here's my code:

plot(HML, type="l", lwd=2, col="red", ylab= "% return")
abline(h = 0, col = "black", lty = "solid")

Any help much appreciated.

Best regards, Martin

Solution 1

First, create a time series object! (using ts())

Then plot, I guess R will show only years on X-axis automatically!

#make Time to time series object
a<-ts(rnorm(150),start=c(2002,7),freq=12);a
plot(a, type="l", lwd=2, col="red", ylab= "% return",xlim=c(2002,2014),axes=F)
axis(1,at=2002:2014,labels=2002:2014);axis(2);box()

Explain code:

1. start in ts() means the times of the first observation
2. freq means the number of observations per unit of time.
3. We can control the range of X-axis by xlim!
4. I don't know how to show all years by code easily,but a stupid method I always use is create one by myself. Hence, adding axes=F in plot means do not show the default axis. Then, create what axis I hoped by axis() and label show all years!
5. Finally, make a box around your picture!

BTW You can find more details by typing ?ts in R !

Solution 2

Read in the data using read.zoo and class "yearmon" (which represents a year and month) for the index. Then plot it using xaxt="n" to suppress the axis. Finally produce the axis yourself using axis to force years only:

Lines <- "Time   HML
200207 6.28 
200208 3.44
200209 8.03
201412 1.47"

library(zoo)
HML <- read.zoo(text = Lines, header = TRUE, FUN = as.yearmon, format = "%Y%m",
 colClasses = c("character", NA))

plot(HML, xaxt = "n", type = "o", xlab = "Year")
rng <- range(floor(time(HML)))
axis(1, rng[1]:rng[2])

Continued after image.

Note 1: If you already have the data as a data frame DF

DF <- read.table(text = Lines, header = TRUE)

then you could replace the read.zoo statement with:

HML <- zoo(DF$HML, as.yearmon(as.character(DF$Time), "%Y%m"))

Note 2: I can't tell whether the actual data has data for every month from the first to the last but the above work even if not.

Solution 3

There are many ways to achieve this... Here is one of them. We'll be using hypothetical data spanning from 2002-01 to 2012-12 (having gaps doesn't matter in this case). Note that we've used the 1st of each month to have a complete date, easily recognizable by the function as.POSIXct which will convert strings to time objects.

Time <- c("2002-01-01", "2002-02-01", "2003-03-01", "2003-04-01", 
          "2004-05-01", "2004-06-01", "2005-07-01", "2005-08-01", 
          "2006-09-01", "2006-10-01", "2006-11-01", "2008-01-01", 
          "2008-02-01", "2009-02-01", "2009-03-01", "2010-04-01", 
          "2010-05-01", "2010-06-01", "2011-07-01", "2011-08-01", 
          "2012-09-01", "2012-10-01", "2012-11-01", "2012-12-01")

HML <- rnorm(n = 24, mean = 6, sd = 2)

dat <- data.frame(Time=as.POSIXct(Time), HML)
rm(Time, HML)

And then use the plot function:

plot(HML ~ Time, type="l", col="red", lwd=2, ylab= "% return", data=dat)

Solution 4

Using ggplot2 would give you a lot of options. The autoplot function accepts and plots zoo objects.

library(ggplot2)
library(magrittr)
library(zoo)

hml_ts <-
  ts(rnorm(150),start=c(2002,7),freq=12)

hml_zoo <-
  as.zoo(hml_ts)

gg <-
  hml_zoo %>%
    autoplot() + 
    xlim(c(2002, end(hml_zoo)))

gg

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