R help - Sep 2016 - ggplot2: geom_segment does not produce the color I desire?

Hi,

   I have a dataset "test". I try to produce a "green" arrow
but it gives a
"red" arrow (as attached). Could someone tell me how I can fix it?
Thanks,
> test
        date    co       y1       y2
5 2011-11-28 green 196.6559 1.600267
> dput(test)
structure(list(date = structure(15306, class = "Date"), co =
"green",
    y1 = 196.655872, y2 = 1.600267), .Names = c("date",
"co",
"y1", "y2"), class = "data.frame", row.names =
5L)
> ggplot()+    geom_segment(mapping = aes(x =
as.Date(test[,"date"]), y y1, xend = as.Date(test[,"date"]),
yend = y2, color=co), data=test,
arrow=arrow())
>
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ggplot will assign, or map if you will, the color based on the default
color scale when color is specified with the mapping argument such as
mapping = aes(color=...). You have two options:

1. if you want the color of your arrow to be based on a column in your
data, then manually scale the color with
scale_colour_manual(values=c('green')):
ggplot()+
geom_segment(mapping = aes(x = as.Date(test[,"date"]), y = y1, xend
as.Date(test[,"date"]), yend = y2, color=co), data=test,
arrow=arrow())+
scale_colour_manual(values=c('green'))

2. If the color doesn't need to be "mapped" based on your data,
then you
can simply specify colour *outside* the aes() like this:
ggplot()+
geom_segment(mapping = aes(x = as.Date(test[,"date"]), y = y1, xend
as.Date(test[,"date"]), yend = y2), color='green', data=test,
arrow=arrow())

keep in mind that only the first option will produce a legend, if you need
that.



On Friday, September 16, 2016, John <miaojpm at gmail.com> wrote:
> Hi,
>
>    I have a dataset "test". I try to produce a "green"
arrow but it gives a
> "red" arrow (as attached). Could someone tell me how I can fix
it? Thanks,
>
> > test
>         date    co       y1       y2
> 5 2011-11-28 green 196.6559 1.600267
> > dput(test)
> structure(list(date = structure(15306, class = "Date"), co =
"green",
>     y1 = 196.655872, y2 = 1.600267), .Names = c("date",
"co",
> "y1", "y2"), class = "data.frame", row.names
= 5L)
> > ggplot()+    geom_segment(mapping = aes(x =
as.Date(test[,"date"]), y > y1, xend =
as.Date(test[,"date"]), yend = y2, color=co), data=test,
> arrow=arrow())
> >
>
	[[alternative HTML version deleted]]

Here are 2 solutions to you problem:

If you only want to use one color (for possibly many arrows),
this will work:

ggplot()+geom_segment(mapping = aes(x = as.Date(test[,"date"]),
                                    y =y1,
                                    xend = as.Date(test[,"date"]),
                                    yend = y2), color="green",
data=testdf,
                      arrow=arrow())


if you use a variable to colors different items differently,
you are using a mapping.
If you want to override ggplot?s default mapping, you set the palette
explicitly:

ggplot()+geom_segment(mapping = aes(x = as.Date(test[,"date"]),
                                    y =y1,
                                    xend = as.Date(test[,"date"]),
                                    yend = y2, color=co), data=testdf,
                                    arrow=arrow()) +
      scale_color_manual(values=list(green="green"))

> On Sep 17, 2016, at 00:43, John <miaojpm at gmail.com> wrote:
> 
>> 
>> test
>        date    co       y1       y2
> 5 2011-11-28 green 196.6559 1.600267
>> dput(test)
> structure(list(date = structure(15306, class = "Date"), co =
"green",
>    y1 = 196.655872, y2 = 1.600267), .Names = c("date",
"co",
> "y1", "y2"), class = "data.frame", row.names
= 5L)
>> ggplot()+    geom_segment(mapping = aes(x =
as.Date(test[,"date"]), y > y1, xend =
as.Date(test[,"date"]), yend = y2, color=co), data=test,
> arrow=arrow())
> 
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