tune the parameter k of the knn algorithm used in imputation.
tune.knn.impute(data, cat.var = 1:ncol(data), k.min = 1, k.max = 20,
frac.miss = 0.1, n.iter = 20, seed = 0)
a data frame
vector containing the categorical variables
minimum value for k
maximum value for k
fraction of missing values to add
number of iterations for each k
random seed
matrix of error distributions