I have three timestamped measurement series, taken over the same interval, but with different actual timestamps. I'd like to show these three trajectories in a combined plot, but because the x-axis (timestamps) is different in each case, I'm having some trouble. Is there a way to do this without picking an x-axis to use and interpolating the y-values for the other two measurement series? I'm fairly new to R, but I feel like there's something obvious I'm overlooking.
For example:
Time Value
1.023 5.786
2.564 10.675
3.678 14.678
5.023 17.456
0.787 1.765
1.567 3.456
3.011 5.879
4.598 7.768
1.208 3.780
2.478 6.890
3.823 9.091
5.125 12.769
With base graphics, you can use a combination of plot and points or lines:
dat1 <- data.frame(Time = c(1.023, 2.564, 3.678, 5.023), Value = c(5.786, 10.675, 14.678, 17.456))
dat2 <- data.frame(Time = c(0.787, 1.567, 3.011, 4.598), Value = c(1.765, 3.456, 5.879, 7.768))
dat3 <- data.frame(Time = c(1.208, 2.478, 3.823, 5.125), Value = c(3.780, 6.890, 9.091, 12.769))
with(dat1, plot(Time, Value, xlim = c(0,6), ylim = c(0,20)))
with(dat2, points(Time, Value, col = "red"))
with(dat3, points(Time, Value, col = "green"))
Take a look at ?legend to add a legend. Or, learn ggplot2 and let it handle that part of it for you:
library(ggplot2)
library(reshape)
plotdata <- melt(list(dat1 = dat1, dat2 = dat2, dat3 = dat3), "Time")
qplot(Time, value, data = plotdata, colour = L1)