Converts the standard plpData to a sparse matrix
Value
Returns a list, containing the data as a sparse matrix, the plpData covariateRef and a data.frame named map that tells us what covariate corresponds to each column This object is a list with the following components:
- data
A sparse matrix with the rows corresponding to each person in the plpData and the columns corresponding to the covariates.
- covariateRef
The plpData covariateRef.
- map
A data.frame containing the data column ids and the corresponding covariateId from covariateRef.