Error while plotting a tree with some squirrels using trees package - r

Question

I am using the package trees found here, by #jbaums and explained in this post.
My data are the following:
the tree is composed by
the trunk
Trunk
[1] 13.60415
and the branches
Tree
TreeBranchLength TreeBranchID
1 10.004269 1
2 7.994269 2
3 9.028834 11
4 10.817401 12
5 8.551311 111
6 10.599798 112
7 11.073243 121
8 13.367392 122
9 9.625431 1111
10 10.793569 1112
11 9.896499 11121
12 8.687741 11122
13 7.791180 1211
14 12.506105 1212
15 6.768478 1221
16 10.441796 1222
17 10.751892 1121
18 9.458651 1122
19 10.768509 11221
20 10.150673 11222
21 12.377448 111211
22 12.235136 111212
23 9.074079 11211
24 9.996334 11212
25 9.807019 112221
26 10.895809 112222
27 6.741274 1122211
28 15.841272 1122212
29 5.753920 11222111
30 8.846389 11222112
31 11.925961 112111
32 9.780776 112112
33 8.207965 12221
34 10.079375 12222
the 50 squirrel populations -
Populations
PopulationPositionOnBranch PopulationBranchID ID
1 10.6321655 112111 1
2 1.0644897 1 2
3 3.9315473 1 3
4 1.0310244 0 4
5 9.1768846 0 5
6 13.4267181 0 6
7 7.9461528 0 7
8 6.0533401 121 8
9 2.1227425 121 9
10 1.8256787 121 10
11 4.7332588 11222112 11
12 4.4837432 11222112 12
13 4.6200834 11222112 13
14 2.5622276 1221 14
15 1.2446683 1221 15
16 7.0674052 111 16
17 1.3854674 111 17
18 4.8735635 111 18
19 9.5007998 1222 19
20 6.6373468 1222 20
21 12.6757728 122 21
22 4.2685465 122 22
23 3.9806540 2 23
24 3.1025403 2 24
25 3.9119065 11122 25
26 1.5527653 11122 26
27 1.6687957 11122 27
28 8.0697456 1122 28
29 6.7871391 1122 29
30 9.8050713 111212 30
31 8.5226920 111212 31
32 3.6113379 111212 32
33 7.3184965 111211 33
34 8.6142984 111211 34
35 1.3550870 1211 35
36 8.3650639 12 36
37 4.6411446 112112 37
38 3.2985541 112112 38
39 12.2344148 1212 39
40 9.0290776 1212 40
41 1.3900249 1121 41
42 0.9261425 1122212 42
43 15.2522199 1122212 43
44 4.0253771 12222 44
45 8.7507678 11222 45
46 4.6289841 1122211 46
47 9.1799522 112 47
48 5.1293838 12221 48
49 1.1543080 12221 49
50 10.1014837 112222 50
the code to produce the plot
g <- germinate(list(trunk.height=Trunk,
branches=Tree$TreeBranchID,
lengths=Tree$TreeBranchLength),
left='1', right='2', angle=30))
xy <- squirrels(g, Populations$PopulationBranchID, pos=Populations$PopulationPositionOnBranch,
left='1', right='2', pch=21, bg='white', cex=3, lwd=2)
text(xy$x, xy$y, labels=seq_len(nrow(xy)), font=1)
, which produces
As you can see on the plot bellow population 43 (blue arrow) is out of the tree.. It seems that the length of the branches on the plot do not correspond to the data. For example the branch (left green arrow) on which are populations 38 and 37 is longer than the one where population 43 is (right green arrow), that is not the case in the data. What am I doing wrong? Have I understood correctly how to use trees?

Answer 1

On studying the germinate function it seems to me that the Tree values that you are passing to it needs to be sorted on TreeBranchId field in the ascending order.
The BranchID: 1122212 where you have placed 43 is not the actual 1122212 branch.
Due to the order in which you have fed the values in the Tree, the function is somehow messing the location of branch.
I was curious to see if I increase the length of Branch ID: 1122212, will it change the branch where 43 is placed, and guess what? it didn't. The branch which actually showed an increase in length was the branch where you have placed 37 and 38.
So this hint pointed out that something was wrong with germinate function. On further debugging I was able to make it work using the below code.
Tree<-read.csv("treeBranch.csv")
Tree<-Tree[order(Tree$TreeBranchID),]
g <- germinate(list(trunk.height=15,
branches=Tree$TreeBranchID,
lengths=Tree$TreeBranchLength),
left='1', right='2', angle=30)
xy <- squirrels(g, Populations$PopulationBranchID,pos=Populations$PopulationPositionOnBranch,
left='1', right='2', pch=21, bg='white', cex=3, lwd=2)
text(xy$x, xy$y, labels=seq_len(nrow(xy)), font=1)