[R] ggplot pale colors

[Victor Gabillon]

Hi Ista,

Thank you so much for your explanation!!
I know now how to handle this scale_color_manual() function.


Le 28/05/2011 19:56, Ista Zahn a écrit :
> Hi Victor,
> The problem is that you have not grasped the difference between
> setting an aesthetic to a fixed value and mapping it to a variable.
> See below for details.
>
> On Sat, May 28, 2011 at 6:16 AM, Victor Gabillon
> <victor.gabillon at inria.fr>  wrote:
>> Hello i am new to ggplot and i observed a strange behavior.
>>
>> I want to display two groups of points, each group with a different color.
>> But i encountered a problem with the colors.
>>
>> Here is a first example:
>>
>> dataset<- data.frame(Main = c("A", "A", "B", "B"), Detail = c( "b", "c", "1", "2"), resp = runif(4, min = 0.5, max = 1))
>>
>> ggplot(dataset, aes(x = Detail, y = resp)) +
>> facet_grid(.~Main, scales = "free_x")+ geom_point(aes( size=6,shape = c(16,16,15,15) ),colour="blue")+geom_hline(aes(yintercept=0.25),colour='blue', size=2)
>>
>> with this code all the point are blue (like the line below)
>>
>>
>> But if i try the following code, where my goal is to have the point on the left blue and the one on the right red, a problem appears:
>>
>> dataset<- data.frame(Main = c("A", "A", "B", "B"), Detail = c( "b", "c", "1", "2"), resp = runif(4, min = 0.5, max = 1))
>>
>> ggplot(dataset, aes(x = Detail, y = resp)) +
>> facet_grid(.~Main, scales = "free_x")+ geom_point(aes( size=6,shape = c(16,16,15,15) ,colour=c("blue","blue","red","red")))+geom_hline(aes(yintercept=0.25),colour='blue', size=2)
>>
> The colors are not coming from c("blue", "blue", "red", "red"). Try this to see
>
> p<- ggplot(dataset, aes(x = Detail, y = resp)) +
> facet_grid(.~Main, scales = "free_x") +
>    geom_point(aes(shape = c(16,16,15,15)
> ,colour=c("purple","purple","foo","foo")), size = 6) +
>    geom_hline(aes(yintercept=0.25),colour='blue', size=2)
> p
>
> So now you see that you are not setting the colors to be red and blue,
> you are mapping the color to a variable that just happens to have
> levels "red" and "blue". The actual colors that are mapped to that
> variable are determined by scale_colour_discrete, as you can see from
>
> p + scale_color_manual(value=c("red", "blue"))
> p + scale_color_manual(value=c("green", "black"))
>
> As a general rule, if you want an aesthetic (e.g., color, size, shape
> etc.) to vary (i.e., to have more than one value) you should put it as
> an argument to aes(). If you just want to set it to a fixed value you
> should set it as an argument to geom_* or as an argument to ggplot()
> itself.
>> The points have different colors but those colors are pale (dull). You can see it by comparing the blue of the points to the blue of the line.
>> I guessing i am duing it wrong but i'm stucked with it.
>>
>> Do you have suggestions?
>>
>> An additional question is that i want to add text along the blue line (which is a reference) but i did not understand what geom_text was expecting.
> see http://had.co.nz/ggplot2/geom_text.html
>
> Best,
> Ista
>> Thanks for your help!
>>
>> Victor
>>
>>
>>
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>>
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>
>