diff --git a/NAMESPACE b/NAMESPACE
index da391da..ee9f374 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -16,6 +16,7 @@ export(updateMFAIR)
 exportClasses(MFAIR)
 exportClasses(MFAIRSingleFactor)
 exportMethods(predict)
+import(Matrix)
 importFrom(dplyr,left_join)
 importFrom(methods,new)
 importFrom(rpart,rpart)
diff --git a/R/mfairObject.R b/R/mfairObject.R
index f8852d2..ee17fef 100644
--- a/R/mfairObject.R
+++ b/R/mfairObject.R
@@ -1,5 +1,13 @@
-#' Each MFAIR object has a number of slots which store information. Key slots to access are listed below.
+#' Define the matrixORdgCMatrix class as the union of matrix and Matrix::dgCMatrix
+#'
+#' @import Matrix
 #'
+setClassUnion(
+  name = "matrixORdgCMatrix",
+  members = c("matrix", "dgCMatrix")
+)
+
+#' Each MFAIR object has a number of slots which store information. Key slots to access are listed below.
 #'
 #' @slot Y A matrix or Matrix::dgCMatrix. The main data matrix of N samples and M features.
 #' @slot X A data.frame. The auxiliary information data frame of N samples and C covariates.
diff --git a/R/mfairUtils.R b/R/mfairUtils.R
deleted file mode 100644
index 8e8d029..0000000
--- a/R/mfairUtils.R
+++ /dev/null
@@ -1,4 +0,0 @@
-#' Defined the matrixORdgCMatrix class as the union of matrix and Matrix::dgCMatrix
-#' @importFrom Matrix dgCMatrix
-#'
-setClassUnion(name = "matrixORdgCMatrix", members = c("matrix", "dgCMatrix"))
diff --git a/man/MFAIR-class.Rd b/man/MFAIR-class.Rd
index 73ea1eb..2b17008 100644
--- a/man/MFAIR-class.Rd
+++ b/man/MFAIR-class.Rd
@@ -13,10 +13,12 @@ Each MFAIR object has a number of slots which store information. Key slots to ac
 \section{Slots}{
 
 \describe{
-\item{\code{Y}}{A matrix. The main data matrix of N samples and M features.}
+\item{\code{Y}}{A matrix or Matrix::dgCMatrix. The main data matrix of N samples and M features.}
 
 \item{\code{X}}{A data.frame. The auxiliary information data frame of N samples and C covariates.}
 
+\item{\code{Y_sparse}}{Logical. Whether the main data matrix Y is stored in the sparse mode.}
+
 \item{\code{Y_center}}{Logical. Whether the main data matrix Y is centered.}
 
 \item{\code{Y_mean}}{Numeric. Mean of the main data matrix Y if centered. Zero if not.}
diff --git a/man/createMFAIR.Rd b/man/createMFAIR.Rd
index d795cbf..6af2ff0 100644
--- a/man/createMFAIR.Rd
+++ b/man/createMFAIR.Rd
@@ -7,7 +7,7 @@
 createMFAIR(Y, X, Y_center = TRUE, K_max = 1L, project = "MFAIR")
 }
 \arguments{
-\item{Y}{A matrix. The main data matrix of N samples and M features.}
+\item{Y}{A matrix or Matrix::dgCMatrix. The main data matrix of N samples and M features.}
 
 \item{X}{A data.frame. The auxiliary information data frame of N samples and C covariates.}
 
diff --git a/man/matrixORdgCMatrix-class.Rd b/man/matrixORdgCMatrix-class.Rd
new file mode 100644
index 0000000..625af45
--- /dev/null
+++ b/man/matrixORdgCMatrix-class.Rd
@@ -0,0 +1,9 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/mfairObject.R
+\docType{class}
+\name{matrixORdgCMatrix-class}
+\alias{matrixORdgCMatrix-class}
+\title{Define the matrixORdgCMatrix class as the union of matrix and Matrix::dgCMatrix}
+\description{
+Define the matrixORdgCMatrix class as the union of matrix and Matrix::dgCMatrix
+}