path.start
Integer. A cluster number indicating the starting cluster that algorithm should use to
build the path. The cluster numbers refer to the plot generated by Fluo_inspection(). Default is 1.
If path.type = "circular" the number does not matter. If path.type = "A2Z" the user should inspect the
Fluo_inspection() plot to detect the beginning of the path. If path.type = "other", the function will
not estimate a path. The user has to manually insert the path progression (the cluster numbers) in
Fluo_modeling() .