Question

I’m trying to plot two time series into the same graph in R.

My data is as follows:

Series 1:

       dates            values
1 2012-09-01 12:00:00   33.6
2 2012-09-05 13:00:00   32.0
3 2012-09-06 15:30:00   30.0
4 2012-09-07 12:45:00   30.0
5 2012-09-08 21:15:00   30.0
6 2012-09-11 15:00:00   28.4

And series 2:

       dates           values
1 2012-09-03 14:05:00  15.6
2 2012-09-05 08:00:00  23.0
3 2012-09-09 15:55:00  19.0
4 2012-09-11 23:00:00  22.0
5 2012-09-14 02:40:00  34.0
6 2012-09-15 12:09:00  29.4

The code that I have is:

var1<-var1[,c("Sampling_Time","Value")]
var2<-var2[,c("Sampling_Time","Value")]

var1$Sampling_Time<- as.POSIXct(var1$Sampling_Time, format="%Y-%m-%d %H:%M:%S")
var2$Sampling_Time<- as.POSIXct(var2$Sampling_Time, format="%Y-%m-%d %H:%M:%S")

plot(var1$Sampling_Time, var1$Value, type= "p" , xlim= NULL, col = "red", size =1,
xlab= "Time",ylab= "Value", main= "Graphic",format="%Y-%b-%d")
par(new=TRUE)
plot(var2$Sampling_Time, var2$Value, type= "p" , xlim= NULL, col = "blue", size =1,
xlab= "Time",ylab= "Value", main= "Graphic",format="%Y-%b-%d")

I would like to plot these two series chronologically with the same x axis for both with the same scale, I mean in one unique chronological x axis.

How might I best accomplish this in R?

Thanks in advance.

Answer 1

You need to define before the limit of the range for x and y in your plot and you need to have the same limit for each plot.

var1S <- c("2012-09-01", "2012-09-05", "2012-09-06", "2012-09-07", "2012-09-08", "2012-09-11")
var1S <- as.Date(var1S, "%Y-%m-%d")
var1T <- c(33.6,32.0,30.0,30.0,30.0,28.4)
var2S <- c("2012-09-03", "2012-09-05", "2012-09-09", "2012-09-11", "2012-09-14", "2012-09-15")
var2S <- as.Date(var2S, "%Y-%m-%d")
var2T <- c(15.6,23.0,19.0,22.0,34.0,29.4)
plot(var1T ~ var1S, type="l",col="red", xlim=range(c(var1S,var2S)), ylim=range(c(var1T,var2T)))
par(new=T)
plot(var2T ~ var2S, type="l",col="green", xlim=range(c(var1S,var2S)), ylim=range(c(var1T,var2T)))