The Sketch Data function specifies an invalid number of selected cells

[haolangchen]

The Sketch Data function usually works properly, but sometimes this situation is encountered. I used the Sketch Data function to filter for a specified cell count, but it returned me the number of cells in the integrated set. How to solve it, what is the situation.

> length(colnames(tmp_seurat))
[1] 4042



test <- SketchData(object = tmp_seurat,ncells = 500,method = "LeverageScore",sketched.assay = "sketch")


> length(colnames(test))
[1] 4042