options(repr.plot.width = 7, repr.plot.height = 6)
options(jupyter.plot_mimetypes = c('application/pdf', 'image/png'))
set.seed(1)
Diffusion Pseudo Time (DPT) is a pseudo time metric based on the transition probability of a diffusion process (Haghverdi et al., 2016).
destiny supports DPT
in addition to its primary function of creating DiffusionMap
s from data.
library(destiny) # load destiny…
data(guo) # …and sample data
library(gridExtra) # Also we need grid.arrange
Registered S3 method overwritten by 'xts': method from as.zoo.xts zoo
DPT
is in practice independent of Diffusion Maps:
par(mar = rep(0, 4))
graph <- igraph::graph_from_literal(
data -+ 'transition probabilities' -+ DiffusionMap,
'transition probabilities' -+ DPT)
plot(
graph, layout = igraph::layout_as_tree,
vertex.size = 50,
vertex.color = 'transparent',
vertex.frame.color = 'transparent',
vertex.label.color = 'black')
However in order not to overcomplicate things, in destiny, you have to create DPT
objects from DiffusionMap
objects.
(If you really only need the DPT, skip Diffusion Component creation by specifying `n_eigs = 0`)
dm <- DiffusionMap(guo)
dpt <- DPT(dm)
The resulting object of a call like this will have three automatically chosen tip cells. You can also specify tip cells:
set.seed(4)
dpt_random <- DPT(dm, tips = sample(ncol(guo), 3L))
Plotting without parameters results in the DPT of the first root cell:
old <- options(repr.plot.width = 14)
grid.arrange(plot(dpt), plot(dpt_random), ncol = 2)
Other possibilities include the DPT from the other tips or everything supported by plot.DiffusionMap
:
grid.arrange(
plot(dpt, col_by = 'DPT3'),
plot(dpt, col_by = 'Gata4', pal = viridis::magma),
ncol = 2
)
options(old)
The DPT
object also contains a clustering based on the tip cells and DPT, and you can specify where to draw paths from and to:
plot(dpt, root = 2, paths_to = c(1,3), col_by = 'branch')
You can further divide branches. First simply plot branch colors like we did above, then identify the number of the branch you intend to plot, and then specify it in a subsequent plot
call. In order to see the new branches best, we specify a dcs
argument that visually spreads out out all four branches.
plot(dpt, col_by = 'branch', divide = 3, dcs = c(-1,-3,2), pch = 20)
Warning message in title(main, sub, ...): “"legend_name" ist kein Grafikparameter” Warning message in plot.xy(xy.coords(x, y), type = type, ...): “"legend_name" ist kein Grafikparameter”