R help - Feb 2008 - Plotting series marked with a symbol on every nth data point, preferably in ggplot...

Hello!

I am working with signals and a plot of several signals on the same
axes can get quite messy. With lines that are very fractured,
distinction by only the linestyle is not very clear. If I add symbols
to the plot however, there are so many symbols, that they overplot and
the whole plot is unreadable once again. I am looking for advice on
how to make a plot with continuous lines and symbols appearing at
every  nth point. An example of this problem and a solution in SAS can
be found here:
www2.sas.com/proceedings/sugi26/p072-26.pdf

The obvious solution would be to extract the n-th point from the
dataset and overplot as a new line with symbols, but this does not
change the legend, does it? How can I then have a line+symbol in the
legend represent my curve?

Now, ideally I would prefer a solution in ggplot, because of the ease
of plotting and changing the plot labels and other properties.
However, I  remember, Hadley mentioned that he is still working on a
new version to have combined line+symbol plots, and probably he hasn't
finished that yet. So any advice is welcome.

Regards,

TL

PS. I did RTFM and I am not posting code, because at this time I
expect a general outline how to do it and what commands to lookup, not
code.

Try this:

pch <- c("+", ""); lwd <- 1
plot(1:10, type = "o", pch = pch, lwd = lwd)
legend("topleft", legend = "data", pch = pch, lwd = lwd)


On Sun, Feb 24, 2008 at 11:01 PM, Tribo Laboy <tribolaboy at gmail.com>
wrote:
> Hello!
>
> I am working with signals and a plot of several signals on the same
> axes can get quite messy. With lines that are very fractured,
> distinction by only the linestyle is not very clear. If I add symbols
> to the plot however, there are so many symbols, that they overplot and
> the whole plot is unreadable once again. I am looking for advice on
> how to make a plot with continuous lines and symbols appearing at
> every  nth point. An example of this problem and a solution in SAS can
> be found here:
> www2.sas.com/proceedings/sugi26/p072-26.pdf
>
> The obvious solution would be to extract the n-th point from the
> dataset and overplot as a new line with symbols, but this does not
> change the legend, does it? How can I then have a line+symbol in the
> legend represent my curve?
>
> Now, ideally I would prefer a solution in ggplot, because of the ease
> of plotting and changing the plot labels and other properties.
> However, I  remember, Hadley mentioned that he is still working on a
> new version to have combined line+symbol plots, and probably he hasn't
> finished that yet. So any advice is welcome.
>
> Regards,
>
> TL
>
> PS. I did RTFM and I am not posting code, because at this time I
> expect a general outline how to do it and what commands to lookup, not
> code.
>
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