how to use a gradient color bar for the legend

[lily li]

Dear ggplot2 users,

I have a question about the legend. For example, my dataset "dataf" is like this:

id  cl   x    y

1   1 2.5 11.0

2   1 4.3 12.0

3   1 2.2 10.0

4   1 5.4  9.0

5   1 6.0 10.0

6   2 7.7  8.0

7   2 7.1  7.8

8   2 2.5  8.9

9   3 5.5  8.8

10  3 4.0 72.0

11  3 4.5  8.0

12  4 6.2 10.0

13  4 7.0 10.5

I use the code to print the points.

plot1 = ggplot(dataf,aes(x=x,y=y,color=factor(cl)))+theme_bw()+ geom_point()

print(plot1)

However, if there are more than 100 classes in the 'cl' column, the legend becomes compact and is not easy to recognize. I'm wondering how to use a gradient color bar to represent the legend? This means that not every 'cl' value is listed in the legend, but just a gradient bar (maybe show the smallest and largest values at the two ends of the bar) to represent the color changes. Thanks for your help in advance.

[Roman Luštrik]

Remove the `factor(cl)` around `cl`. Assuming `cl` is integer/numeric.

Cheers,

Roman

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[lily li]

Hi Roman,

Thanks, it works and shows a gradient bar. Would it be possible to increase the color contrasting? Before, the colors change as a rainbow color, now the points all have a blue color and hard to differentiate. Thanks again.

[Roman Luštrik]

See http://ggplot2.tidyverse.org/reference/scale_gradient.html for more details. 

If you search the internet for "increase contrast gradient ggplot2" or something akin to this, you can find stackoverflow questions like this one:

https://stackoverflow.com/questions/17506336/increasing-contrast-of-ggplot2-scale-colour-gradient-in-r

Cheers,

Roman