R help - May 2018 - Change the legend order by order function

Hi,

  I'd like to graph three lines on ggplot2 and I intend the lines to be
"solid", "dashed", and "dotted". The legend names
are "name_b", "name_c",
"name_a". I'd like to legend to present in the order: the
"name_b" at the
top, and "name_a" at the bottom.

   Could it be done by order function or its inverse?

Thanks,

##### source code

library(ggplot2)

od<-order(c("name_b", "name_c", "name_a"))
df<-data.frame(x1=c(1,2), y1=c(3,4),z1=c(5,6),w1=c(7,8))
p1<-ggplot(df, aes(x=1:2, y=x1))+
  geom_line(aes(linetype="name_b"))+
  geom_line(aes(x=1:2, y=y1, linetype="name_c"), df)+
  geom_line(aes(x=1:2, y=z1, linetype="name_a"), df)+
scale_linetype_manual(name="",
values=c("solid","dashed", "dotted")[(od)],
labels=c("name_b","name_c","name_a"))


#### supplement
> od
[1] 3 1 2
> order(od)
[1] 2 3 1

	[[alternative HTML version deleted]]

There are two key concepts you seem to be unaware of regarding ggplot: 1) you
really need to put your data in long format to work with multiple curves, and 2)
the column containing the names of the curves should be a factor with levels in
the order you wish them to be presented in the legend (bottom to top). I am not
in a position at the moment to give you a full reprex, but Google can probably
help you find lots of examples... try keywords factor long ggplot.

Regarding using order to do this, the answer is likely "yes" but your
existing example order seems easier to do with an explicit listing of labels in
sequence... I cannot fathom why you think name_b, name_c, name_a is a natural
result of using the order function that people will want to see. Either be
explicit or use an alphabetic order, either way does not need the order
function.



On May 23, 2018 10:27:14 AM GMT+02:00, John <miaojpm at gmail.com>
wrote:
>Hi,
>
>  I'd like to graph three lines on ggplot2 and I intend the lines to be
>"solid", "dashed", and "dotted". The legend
names are "name_b",
>"name_c",
>"name_a". I'd like to legend to present in the order: the
"name_b" at
>the
>top, and "name_a" at the bottom.
>
>   Could it be done by order function or its inverse?
>
>Thanks,
>
>##### source code
>
>library(ggplot2)
>
>od<-order(c("name_b", "name_c", "name_a"))
>df<-data.frame(x1=c(1,2), y1=c(3,4),z1=c(5,6),w1=c(7,8))
>p1<-ggplot(df, aes(x=1:2, y=x1))+
>  geom_line(aes(linetype="name_b"))+
>  geom_line(aes(x=1:2, y=y1, linetype="name_c"), df)+
>  geom_line(aes(x=1:2, y=z1, linetype="name_a"), df)+
>scale_linetype_manual(name="",
values=c("solid","dashed",
>"dotted")[(od)],
>labels=c("name_b","name_c","name_a"))
>
>
>#### supplement
>> od
>[1] 3 1 2
>> order(od)
>[1] 2 3 1
-- 
Sent from my phone. Please excuse my brevity.

Hi

Which is actually answer the OP already got.
> library(ggplot2)
> df<-data.frame(x1=c(1,2), y1=c(3,4),z1=c(5,6),w1=c(7,8))
> library(reshape2)
> dfm<-melt(df)
No id variables; using all as measure variables
> dfm$variable<-factor(dfm$variable,
levels=levels(dfm$variable)[c(2,1,3,4)])
> p2<-ggplot(dfm, aes(x=rep(1:2,4), y=value))
> p2+geom_line(aes(linetype=variable))+
+ scale_linetype_manual(values=c("solid", "dashed",
"dotted", "blank"),
+ labels=c("name_b","name_a","name_c",
"other"))
>
Cheers
Petr

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> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Jeff
> Newmiller
> Sent: Wednesday, May 23, 2018 12:56 PM
> To: John <miaojpm at gmail.com>; r-help <r-help at
r-project.org>; David
> Winsemius <dwinsemius at comcast.net>; Rui Barradas <ruipbarradas
at sapo.pt>
> Subject: Re: [R] Change the legend order by order function
>
> There are two key concepts you seem to be unaware of regarding ggplot: 1)
> you really need to put your data in long format to work with multiple
curves,
> and 2) the column containing the names of the curves should be a factor
with
> levels in the order you wish them to be presented in the legend (bottom to
> top). I am not in a position at the moment to give you a full reprex, but
Google
> can probably help you find lots of examples... try keywords factor long
ggplot.
>
> Regarding using order to do this, the answer is likely "yes" but
your existing
> example order seems easier to do with an explicit listing of labels in
sequence...
> I cannot fathom why you think name_b, name_c, name_a is a natural result of
> using the order function that people will want to see. Either be explicit
or use
> an alphabetic order, either way does not need the order function.
>
>
>
> On May 23, 2018 10:27:14 AM GMT+02:00, John <miaojpm at gmail.com>
> wrote:
> >Hi,
> >
> >  I'd like to graph three lines on ggplot2 and I intend the lines
to be
> >"solid", "dashed", and "dotted". The
legend names are "name_b",
> >"name_c", "name_a". I'd like to legend to
present in the order: the
> >"name_b" at the top, and "name_a" at the bottom.
> >
> >   Could it be done by order function or its inverse?
> >
> >Thanks,
> >
> >##### source code
> >
> >library(ggplot2)
> >
> >od<-order(c("name_b", "name_c",
"name_a")) df<-data.frame(x1=c(1,2),
> >y1=c(3,4),z1=c(5,6),w1=c(7,8)) p1<-ggplot(df, aes(x=1:2, y=x1))+
> >  geom_line(aes(linetype="name_b"))+
> >  geom_line(aes(x=1:2, y=y1, linetype="name_c"), df)+
> >  geom_line(aes(x=1:2, y=z1, linetype="name_a"), df)+
> >scale_linetype_manual(name="",
values=c("solid","dashed",
> >"dotted")[(od)],
> >labels=c("name_b","name_c","name_a"))
> >
> >
> >#### supplement
> >> od
> >[1] 3 1 2
> >> order(od)
> >[1] 2 3 1
>
> --
> Sent from my phone. Please excuse my brevity.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Jeff
Newmiller
> Subject: Re: [R] Change the legend order by order function
> 
> [snip]
>
> I cannot fathom why you think name_b, name_c, name_a is a
> natural result of using the order function that people will want to see.
Either
> be explicit or use an alphabetic order, either way does not need the order
> function.
Things like 'high', 'med', 'low' also often need some
care to avoid an inappropriate alphabetical ordering.

ggplot (like many base graphics) will typically sort and display by level order
in a factor, not alphabetically.

So the key is to set the factor levels in the appropriate order in the first
place. If you define the factor level order explicitly on creating the factor,
as in
gp <- factor(<a vector>,  levels=c("name_b",
"name_c", "name_a"))
#or, for a more obviously likely example
lmh <- factor(sample(c("High", "Medium",
"Low"), 30, replace=T),  levels=c("Low", "Medium",
"High"))

ggplot will then display legends etc in the defined and now appropriate factor
level order by default.

S Ellison


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