Compute degrees of freedom according to the Barnard-Rubin formula.
rubin_df(v_com, var_b, var_t, M)Degrees of freedom according to Barnard-Rubin formula. See Barnard-Rubin (1999).
Positive number representing the degrees of freedom in the complete-data analysis.
Between-imputation sample variance of the point estimates across multiply imputed datasets.
Estimate (according to Rubin's rules) of the variance of the point estimates.
Number of imputations (integer larger than 1).
The computation takes into account limit cases where there is no missing data
(i.e. the between-variance var_b is zero) or where the complete-data degrees of freedom is
set to Inf. Moreover, if v_com is given as NA, the function returns Inf.
Barnard, J. and Rubin, D.B. (1999). Small sample degrees of freedom with multiple imputation. Biometrika, 86, 948-955.