R help - Dec 2019 - Adding a legend to a (multi-facet) plot produced by ggplot().

I have been struggling to add a legend as indicated in the subject line,
with no success at all.  I find the help to be completely bewildering.

I have attached the code of what I have tried in the context of a simple
reproducible example.

I have also attached a pdf file of a plot produced with base graphics to 
illustrate roughly what I am after.

I would be grateful if someone could point me in the right direction.

cheers,

Rolf Turner

-- 
Honorary Research Fellow
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276

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Hello,

See if this is it. The standard trick is to reshape the data from wide 
to long, see the SO post [1]. Then add a scale_shape_* layer to the plot.


yyy <- cbind(xxx, y3 = y3)
long <- reshape2::melt(yyy, id.vars = c("x", "y1",
"grp"))

ggplot(long, aes(x, y = value, colour = variable, shape = variable)) +
   geom_line(aes(y = y1)) +
   geom_point() +
   scale_colour_manual("Doesn't
work",values=c("blue","red"),
                       labels=c("clyde","irving")) +
   scale_shape_manual("Doesn't work",values=c(16,3),
                       labels=c("clyde","irving")) +

   facet_grid(cols=vars(grp))


[1] 
https://stackoverflow.com/questions/2185252/reshaping-data-frame-from-wide-to-long-format

Hope this helps,

Rui Barradas

?s 00:04 de 01/12/19, Rolf Turner escreveu:
> 
> I have been struggling to add a legend as indicated in the subject line,
> with no success at all.? I find the help to be completely bewildering.
> 
> I have attached the code of what I have tried in the context of a simple
> reproducible example.
> 
> I have also attached a pdf file of a plot produced with base graphics to 
> illustrate roughly what I am after.
> 
> I would be grateful if someone could point me in the right direction.
> 
> cheers,
> 
> Rolf Turner
> 
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
>

On 2/12/19 3:03 am, Rui Barradas wrote:
> Hello,
> 
> See if this is it. The standard trick is to reshape the data from wide 
> to long, see the SO post [1]. Then add a scale_shape_* layer to the plot.
> 
> 
> yyy <- cbind(xxx, y3 = y3)
> long <- reshape2::melt(yyy, id.vars = c("x", "y1",
"grp"))
> 
> ggplot(long, aes(x, y = value, colour = variable, shape = variable)) +
>  ? geom_line(aes(y = y1)) +
>  ? geom_point() +
>  ? scale_colour_manual("Doesn't
work",values=c("blue","red"),
>  ????????????????????? labels=c("clyde","irving")) +
>  ? scale_shape_manual("Doesn't work",values=c(16,3),
>  ????????????????????? labels=c("clyde","irving")) +
> 
>  ? facet_grid(cols=vars(grp))
> 
> 
> [1] 
>
https://stackoverflow.com/questions/2185252/reshaping-data-frame-from-wide-to-long-format
> 
> 
> Hope this helps,
Almost there.  However the colour of the line changes with "values"
and
lines show up in the legend.  I want the lines to be black in all 
facets, and only points to show up in the legend.

I fiddled about a bit trying to achieve this but only succeeded in 
messing things up completely.

Can you guide me a bit further, please?

cheers,

Rolf

-- 
Honorary Research Fellow
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276