1. download monocle from https://www.bioconductor.org/packages/3.15/bioc/src/contrib/Archive/monocle/
2. decompress the package 'monocle_2.24.0.tar.gz', and get a 'monocle' folder.
3. open the folder 'monocle/R', change the code in function 'project2MST()' in the 'order_cell.R' file: change from
if(class(projection) != 'matrix')
projection <- as.matrix(projection)
to
projection <- as.matrix(projection)
