Standardize the variables within a range [-1.0 and 1.0]

        This replaces the local copies of this data. When it's time to
        scale back, use destandardize from the datasource for that.

def standardize(self):
        """Standardize the variables within a range [-1.0 and 1.0]

        This replaces the local copies of this data. When it's time to
        scale back, use destandardize from the datasource for that.

        """
        self.covariates = self.datasource.covariate_data
        self.phenotypes = self.datasource.phenotype_data