## Usage

subset_matrix(s, mat, colname = "SampleID")

## Arguments

- s
- a sample data dataframe
- mat
- a counts matrix
- colname
- the name of the column to use for subsetting

## Value

the subsetted matrix

## Description

This is useful for subsetting a counts matrix based on the sample IDs present
in the sample data dataframe. It then prunes the matrix to remove any rows
whose sums are 0.