music_Sigma: Cross-subject Varirance of Relative Abudance
In kalpita23/scRNA_package: Multi-subject single cell deconvolution

This function is for calculating the cross-subject variance of relative abundance for selected cell types.

1	music_Sigma(x, non.zero, markers, clusters, samples, select.ct)

`x`	ExpressionSet, single cell dataset
`non.zero`	logical, if true, remove all gene with zero expression
`markers`	vector or list of gene names
`clusters`	character, the phenoData used as clusters
`samples`	character,the phenoData used as samples
`select.ct`	vector of cell types included, default as `NULL`. If `NULL`, include all cell types in `x`