[R] Enquiries about time plots in R
p.pagel at wzw.tum.de
Wed Nov 12 17:06:47 CET 2008
> I am trying to do some time plots with R but it seems that it
> is not working. The problem is that the time is not regular,
> for example, a small dataset can be seen below:
> Date pH
> 1/02/1998 5.5
> 5/03/1998 5
> 8/12/1998 6
> 1/02/1999 6.1
> 08/10/2000 7.2
> I have used the function >plot(DATE, pH) and then >lines(pH),
> but the line does not join the points.
lines() needs the same arguments as plot().
> I have used many combinations, e.g. >plot(DATE, pH) and then
> >lines(DATE, pH), where I get a plot with full of lines inside
You are on the right track here. You probably want something like
plot(Date, ph, type="l")
plot(Date, ph, type="b")
R will plot in the order of appearance, so you may want to sort
the data.frame before plotting.
> x-axis I do not have the DATE. It says Index from 0 to 80.
Have a look at the structure of your data. str() will do that for
you. I suspect that Date is a factor rather than a Date. Use
as.Date() to fix that.
> Do you know if there is a function where I can have in x-axis
> the DATE (irregular dates) and in y-axis the variable with a
> continuous line, showing how it changes through time?
So in summary you probably want something like this:
# make some example data
df <- data.frame(
y=c(12.5, 17, 13.6, 23.345)
# convert to Date, sort and plot
df$d <- as.Date(df$d)
df <- df[order(df$d), ]
Dr. Philipp Pagel
Lehrstuhl für Genomorientierte Bioinformatik
Technische Universität München
85350 Freising, Germany
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