allocateCells           Annotate all cells with contour level of cell
                        type-specific density.
cellsInRegion           Check which cells are in which regions
computeDensity          Perform kernel density estimation on
                        SpatialExperiment
contour2sf              Draw a contour region on some density level
corDensity              Test for density correlation between two cell
                        types.
findROI                 Find ROIs based on cell type-specific densities
                        via graph-based method.
getContour              Get contour from density
getContourRegions       Calculate areas between every two density
                        levels
grid2sf                 Combine grids in each ROI to a sf region
gridDensity             Perform kernel density estimation on
                        SpatialExperiment for cell types of interest
mergeROI                Manually merge ROIs
plotCellCompo           Plot cell type composition in each density
                        level of cell of interest.
plotContour             Plot contour lines.
plotContourRegion       Visualising an sf object (for internal use only
                        at the moment)
plotCorHeatmap          Plot model statistics using heatmap.
plotDensCor             Plot density correlation between two cell types
plotDensity             Plot grid-based density.
plotROI                 Plot ROIs on spatial.
plotSpatial             Plot cells based on spatial coordinates.
postSelRegion           Merge sel_region from the selectRegion function
                        to SpatialExperiment.
selectRegion            Select region of interest from plot
spe2PB                  Given a 'SpatialExperiment' data object, create
                        pseudo-bulk samples using the colData
                        information and return a DGEList object
