aux.rndmissing          Randomly assign NAs to the data matrix with
                        probability 'x'
fill.HardImpute         HardImpute : Generalized Spectral
                        Regularization
fill.KNNimpute          Imputation using Weighted K-nearest Neighbors
fill.OptSpace           OptSpace
fill.SVDimpute          Iterative Regression against Right Singular
                        Vectors
fill.SVT                Singular Value Thresholding for Nuclear Norm
                        Optimization
fill.SoftImpute         SoftImpute : Spectral Regularization
fill.USVT               Matrix Completion by Universal Singular Value
                        Thresholding
fill.nuclear            Low-Rank Completion with Nuclear Norm
                        Optimization
fill.simple             Imputation by Simple Rules
lena128                 lena image at size of (128 \times 128)
lena256                 lena image at size of (256 \times 256)
lena64                  lena image at size of (64 \times 64)
