ggparcoord: color using discrete scale

Question

I cannot seem to get my ggparcoord plot to color using a discrete scale. When I do this:

ggparcoord(data = iris, columns = 1:4, groupColumn = "Species")

the output plot is still coloring the lines using a continuous scale (using the levels of the Species factor).

I've also tried a modified version of the the scale_color_manual trick specified here: controlling color in ggparcoord, to no avail.

ggparcoord(data = iris, columns = 1:4, groupColumn = "Species") + 
    scale_color_manual(values = c("setosa" = "red", 
                                  "versicolor" = "green", 
                                  "virginica" = "blue"))

But I get this error message: Error: Continuous value supplied to discrete scale.

I've also tried .. + scale_color_discrete(): same error message.

I'm stumped... even the examples on the ggparcorod cran page aren't working:

data(diamonds, package="ggplot2")
diamonds.samp <- diamonds[sample(1:dim(diamonds)[1],100),]
ggparcoord(data = diamonds.samp,columns = c(1,5:10),groupColumn = 2)

Error message: Error: (list) object cannot be coerced to type 'double'

Edit

There is a solution to this which is to use mapping=aes(color=as.factor(Species)), as shown in Didzis Elferts' answer below. But, it requires adding some further customizations in scale_color_discrete

ggparcoord(data = iris, columns = 1:4, mapping=aes(color=as.factor(Species))) +
        scale_color_discrete("Species", labels=levels(iris$Species) )

Is there a method of accomplishing the same thing without needing to add the scale_color_discrete("Species", labels=levels(iris$Species) ) part?

For example, in ggplot2,

ggplot(data=iris, aes(x=Sepal.Width,y=Sepal.Length,color=Species)) + geom_point()

automatically generates nicely labeled legends. Is there an analogous method in ggparcoord?

I am using R version 3.2.1, ggplot2_2.0.0, and GGally_1.0.0

sessionInfo()
# R version 3.2.1 (2015-06-18)
# Platform: x86_64-apple-darwin13.4.0 (64-bit)
# Running under: OS X 10.10.5 (Yosemite)
# 
# locale:
# [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
# 
# attached base packages:
# [1] stats     graphics  grDevices utils     datasets  methods   base     
# 
# other attached packages:
# [1] ggplot2_2.0.0 GGally_1.0.0  magrittr_1.5  dplyr_0.4.3  

Any help would be much appreciated!

Answer 1

One solution is to use argument mapping= and set it to as.factor(Species) (without as.factor() it gives the same result as in question). Then with scale_color_discrete() you can get Species names as labels.

ggparcoord(data = iris, columns = 1:4, mapping=aes(color=as.factor(Species)))+
  scale_color_discrete("Species",labels=levels(iris$Species))