This functions imputes interval data variables. Those are variables,
that consists of a lower and upper (numeric) boundary. Technically
those boundaries are contained in a string, separated by a semi colon.
E.g. if a person reports there income to be something between 3000 and 4000 dollars,
its value in the interval covariate would be "3000;4000".
Left (resp. right) censored data can be denoted by "-Inf;x" (resp. "x;Inf"),
with x being the (numeric) observed value.
imp_interval(y_imp, X_imp, pvalue = 0.2, k = Inf)A Vector from the class interval with the variable to impute.
A data.frame with the fixed effects variables.
A numeric between 0 and 1 denoting the threshold of p-values a variable in the imputation model should not exceed. If they do, they are excluded from the imputation model.
An integer defining the allowed maximum of levels in a factor covariate.
A n x 1 data.frame with the original and imputed values.
Note that this function won't return interval data as its purpose is to
"break" the interval answers into precise answers.