[R] different data series on one graph

[Achim Zeileis]

wouter.buytaert at yucom.be wrote:
> 
> Hello,
> 
> I'm looking for a way to plot different data series on one graph.
> I have a series of hourly rainfall and quarterly flow
> measurements (i.e. 4 times an hour) of a catchment. The rainfall
> should be plotted in bars, the flow as a line. Both on the same X
> axe (time) but with different Y axes.
> 
> The problem is the plot() function does not support add=TRUE...
> 
> Furthermore I'm not sure what's the best format for input data.
> Now it are two data frames with a time (POSIXct) and a
> rainfall/flow part. Maybe time series are easier, but in
> 
> ts(data = NA, start = X,...
> 
> X should be a number or a vector. how does this coresponds to a
> data and hour (e.g. april 26,2002, 15:00:00)?

If your observations are equidistant, e.g. you've got 24 hourly
measurements per day, you could do something like this for the above
example:

R> rain <- ts(rain, start = c(26, 15), freq = 24)
R> flow <- ts(flow, start = c(26, 15), freq = 96)
and then you can just do

R> plot(rain)
R> lines(flow, col = 2)
for a time series plot.

If the observations are not equally spaced, then it is probably the
easiest thing to get a vector of dates on a reasonable scale (days or
something like that) and then do:

R> plot(time.rain, rain, type = "l")
R> lines(time.flow, flow, col = 2)

Hope this helps
Z

> Thanks,
> 
> Wouter Buytaert
> Institute for Land and Water Management
> Katholieke Universiteit Leuven
> 
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