Support plotting trajectory curves on dittoDimPlot about dittoseq HOT 2 CLOSED

I do not currently, but am open to suggestions for how I might do so.

dittoDimPlot currently allows plotting of trajectories over any dimensionality reduction using straight lines between clusters in the trajectory paths. That is as far as I had planned because median cluster centers are easy to calculate, and afterwards, the method for making a straight line between points is unambiguous. There is little methods ambiguity here except in that median is what's used for picking the clusters' centers.

Currently, as far as I have experience at least, trajectory analysis packages tend to only calculate smoothed curves for certain dimensionality reductions. Because there are many options for how to calculate such curves, I do not plan to make dittoSeq into a calculation tool for new curve paths at this time.

That said, I supposed a method for extraction and plotting of calculated curves is possible. geom_path is the geom already used for plotting trajectories, so I suppose that all adding this feature would require conceptually is a method to accept manually provided paths. Perhaps with a list structure similar to the current add.trajectories but with:

• add.manual.trajectories.x & add.manual.trajectories.y = list of vectors, one for each separate trajectory, of x and y coordinates, that the curves should follow
• manual.trajectory.arrow.size = size of the arrows

Does that sound like a useful method?

from dittoseq.

I've submitted #19 to handle this for slingshot output. Does no calculations, just grabs the curve coordinates and plots them.

from dittoseq.