[R] legend question

[Jenny Barnes]

Hi folks,

Do you mind if I ask a related question that I have been having trouble with - 
how do you put the legend outside of the plot area (to the bottom of the area - 
below the x-axis title)? Could anybody show me using the example given below:

x <- seq(-pi, pi, len = 65)
plot(x, sin(x), type="l", col = 2)
legend(x = -3, y = .9, "legend text", pch = 1, xjust = 0.5)

Thank you, I've not been able to do this simple bit of programming and it is 
very frustrating not to be able to add a simple key.

Best Wishes,

Jenny

Hi Emili,

Even though you are calling your horizontal coordinate y, and vertical
coordinate z, the first and second arguments to legend(), namely x and y,
should be the horizontal and vertical coordinates, respectively; and they are
given in user coordinates (e.g., legend()'s x should be between 1960 and 1975
and legend()'s y should be between 1 and 4).

If you want to use normalized coordinates (i.e. 0 to 1), you can scale as in
this example:

legend(x = par("usr")[1] + diff(par("usr")[1:2])*normalizedCoordX,
       y = par("usr")[3] + diff(par("usr")[3:4])*normalizedCoordY,
       ...)

where normalizedCoordX and Y go from 0 to 1 (see ?par, par("usr") returns
vector of c(xmin,xmax,ymin,ymax) of user coordinates on a plot)

You can alternatively use legend(x = "topleft",...) or "bottomright", and so
on to place your legend.

If you want to add your legend outside of the plot, you should consider
increasing the margins using the 'mar' argument in par(), and also setting
par(xpd=TRUE) (so stuff can show up outside of the plotting region).

Best regards,
ST


> y<-c(1960, 1965, 1970, 1975)
> z<-c(1, 2, 3, 4)
within the data limits of your x and y)





--- Emili Tortosa-Ausina <Emili.Tortosa at eco.uji.es> wrote:

> Hi to all,
> 
> I'm sorry for posting this question, I am sure I am missing something 
> important but after reading the documentation I cannot find where the 
> problem is.
> 
> I want to add a legend to a figure. If I use a simple example drawn 
> from the R Reference Manual such as, for instance:
> 
> x <- seq(-pi, pi, len = 65)
> plot(x, sin(x), type="l", col = 2)
> legend(x = -3, y = .9, "legend text", pch = 1, xjust = 0.5)
> 
> then everything works just fine.
> 
> However, if I use other data such as, for instance:
> 
> y<-c(1960, 1965, 1970, 1975)
> z<-c(1, 2, 3, 4)
> plot(y, z, type="l", col = 2)
> legend(x = -3, y = .9, "legend text", pch = 1, xjust = 0.5)
> 
> then the legend is not shown.
> 
> Any hints?
> 
> Thanks in advance,
> 
> Emili
> 
> ______________________________________________
> R-help at stat.math.ethz.ch 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.
> 



 
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jennifer Barnes
PhD student: long range drought prediction 
Climate Extremes Group
Department of Space and Climate Physics
University College London
Holmbury St Mary 
Dorking, Surrey, RH5 6NT
Tel: 01483 204149
Mob: 07916 139187
Web: http://climate.mssl.ucl.ac.uk