calBmatCor: Check correlation of cell-by-bin matrix
Description
This function takes one or two snap object as input and calculate
the correlation between cell-by-bin matrix between replicates. If
obj2 is NULL, obj1 will be randomly split into two pseudo replicates
and the correlaion between these two pseudo-replicates will be
calcualted and returned. For obj1, the cell-by-bin matrix
cannot be empty. This function helps check whether the current
cell-by-bin matrix is sufficient for downstream analysis. If the
pearson correlation is less than 0.95 recommend to use a bigger bin.size.