R/wrap_add_root.R
    add_root_using_expression.RdAdd root cell to wrapper using expression of features
add_root_using_expression(trajectory, features_oi, expression_source = "expression")
| trajectory | the trajectory object  | 
    
|---|---|
| features_oi | The feature ids which will be used to root  | 
    
| expression_source | Source of the expression, either a string or a matrix  |