R help - Dec 2007 - plot multiple data sets on same axis

I'm new to R and struggling to reproduce graphs I've made with gnuplot.
Example here:

    http://www.slamb.org/tmp/one-active.png

I have three different data sets plotted on the same axis. (I also have
a number of samples for each X value which I displayed with quartiles
rather than plotting every point; that will likely be the subject of my
next question.)

My attempts to do this in R: I've put the data into a frame with (x, y,
dataset) columns; dataset is a categorical variable. I can get a coplot
which sort of shows the information:

    attach(myframe)
    coplot(y ~ x | dataset)

but not on the same axis with a legend. I'd like to start by getting
that in a scatterplot form:

    # XXX: datasets hardcoded in here...
    # is split() supposed to do something similar to this?
    # or how do I get a list of datasets to feed into subset?
    myframe_a <- subset(myframe, dataset=='a')
    myframe_b <- subset(myframe, dataset=='b')
    ...

and then I can apparently plot one and add points from others to it:

    # XXX: more hardcoding...
    attach(myframe_a)
    plot(x, y, col='red')
    detach(myframe_a)
    attach(myframe_b)
    points(x, y, col='blue')
    detach(myframe_b)
    ...
    legend("topleft",
           legend=c("a", "b", ...),
           fill=c("red", "blue", ...))

but there are several things I don't like about this solution:

* there probably is an existing function which does this? I can't find it.

* obviously I don't want to duplicate code for each dataset. I'd rather
loop based on whatever datasets are in the frame, but I'm missing how to
do that here.

* points() appears to not alter xlim and ylim. Is there a convenient way
to autodetermine them based on all the points?

* I've hardcoded the colors. This is the sort of thing I'd rather leave
to an expert. (I.e. someone who has looked at colorblindness studies and
knows which colors are easiest to distinguish.)

Any ideas?

Cheers,
Scott

Here is one way of doing it by splitting the data and plotting each
set in a different color:

# generate some test data
mydf <- data.frame(x=runif(200), y=rnorm(200),
dataset=sample(LETTERS[1:4], 200, TRUE))
# setup the plot are for the maximum of the data
plot(0, xlim=range(mydf$x), ylim=range(mydf$y), type='n',
ylab="Y", xlab="X")
# split by 'dataset' and then plot each series; sort by 'x'
first
mydf[] <- mydf[order(mydf$x),]
split.df <- split(mydf, mydf$dataset)
# loop through each set and plot with a different color
for (i in seq_along(split.df)){
    lines(split.df[[i]]$x, split.df[[i]]$y, col=i)
}


On Dec 30, 2007 5:11 PM, Scott Lamb <slamb at slamb.org>
wrote:
> I'm new to R and struggling to reproduce graphs I've made with
gnuplot.
> Example here:
>
>    http://www.slamb.org/tmp/one-active.png
>
> I have three different data sets plotted on the same axis. (I also have
> a number of samples for each X value which I displayed with quartiles
> rather than plotting every point; that will likely be the subject of my
> next question.)
>
> My attempts to do this in R: I've put the data into a frame with (x, y,
> dataset) columns; dataset is a categorical variable. I can get a coplot
> which sort of shows the information:
>
>    attach(myframe)
>    coplot(y ~ x | dataset)
>
> but not on the same axis with a legend. I'd like to start by getting
> that in a scatterplot form:
>
>    # XXX: datasets hardcoded in here...
>    # is split() supposed to do something similar to this?
>    # or how do I get a list of datasets to feed into subset?
>    myframe_a <- subset(myframe, dataset=='a')
>    myframe_b <- subset(myframe, dataset=='b')
>    ...
>
> and then I can apparently plot one and add points from others to it:
>
>    # XXX: more hardcoding...
>    attach(myframe_a)
>    plot(x, y, col='red')
>    detach(myframe_a)
>    attach(myframe_b)
>    points(x, y, col='blue')
>    detach(myframe_b)
>    ...
>    legend("topleft",
>           legend=c("a", "b", ...),
>           fill=c("red", "blue", ...))
>
> but there are several things I don't like about this solution:
>
> * there probably is an existing function which does this? I can't find
it.
>
> * obviously I don't want to duplicate code for each dataset. I'd
rather
> loop based on whatever datasets are in the frame, but I'm missing how
to
> do that here.
>
> * points() appears to not alter xlim and ylim. Is there a convenient way
> to autodetermine them based on all the points?
>
> * I've hardcoded the colors. This is the sort of thing I'd rather
leave
> to an expert. (I.e. someone who has looked at colorblindness studies and
> knows which colors are easiest to distinguish.)
>
> Any ideas?
>
> Cheers,
> Scott
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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