Tuesday, January 10, 2017

Overlaying a contMap style continuous character map on a dotTree plot

A phytools user recently posted the following question:

“Is there a blog post / function capable of combining the functionality of contmap and dottree? I'm looking to plot a continuous character with a color ramp on the tree with a discrete character dot next to the tips of the tree. If I there is a post on this I have missed it in my search and would appreciate being pointed in the right direction if it is out there.”

The answer is that this is pretty straightforward to do - though it does take a little investigating of the internals of each function.

Here my approach will be to compute a "contMap" object & then overlay it on top of a plotted dotTree.

We can start by imagining the following data:

## Phylogenetic tree with 26 tips and 25 internal nodes.
## Tip labels:
##  A, B, C, D, E, F, ...
## Rooted; includes branch lengths.
## A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
## c c c b a c c c c c c b a a b b b b b c c c b a a a 
## Levels: a b c
##       A       B       C       D       E       F       G       H       I 
## -0.7592 -0.9114 -1.1249  0.0006 -0.8630  2.5855  2.8233  2.4789  2.3854 
##       J       K       L       M       N       O       P       Q       R 
## -2.5600 -2.3400 -2.3566 -1.8551 -1.6360 -0.4659 -3.1787 -2.8704 -0.0257 
##       S       T       U       V       W       X       Y       Z 
##  0.3514  0.0436  0.9419 -0.2918 -0.6332 -0.5828 -0.3969 -2.1122

Next, we compute our "contMap" object, but we don't plot it:

## Object of class "contMap" containing:
## (1) A phylogenetic tree with 26 tips and 25 internal nodes.
## (2) A mapped continuous trait on the range (-3.1787, 2.8233).

Finally, we plot our discrete character using dotTree after which we overlay our contMap style plot. This is the tricky part because I had to look up & duplicate the internal plotting parameters of dotTree to ensure that the two trees where directly overlain:

add.color.bar(0.3*max(nodeHeights(tree)),obj$cols,title="trait value",

plot of chunk unnamed-chunk-3

That's it!


  1. Is there a way to color the tip names (A, B, C, ...) instead of adding dots in front of the names? Thank you.

  2. Hi Liam, i am really new to R and phylogeny analysis and thank you so much for this. I tried to use these codes for my data (species (A to Z), growth form (a and b), and traits (flowering date), however it showed errors all the time. I wondered how you made x and y values from csv file and in R.


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