add_index(): Regulate case inclusion in index calculation with missing values

[LKobilke]

This feature could allow users to regulate how long a case remains in the index calculation, especially in scenarios where there are many missing values distributed across the variables.

Currently, the add_index function computes a row-wise mean or sum index of specific variables in a dataset, with an option to remove NA values before the computation. However, isn't an option to control the duration a case remains in the computation amidst a considerable amount of missing data across index variables.

An additional argument could be introduced to the function, allowing users to specify a threshold of allowable missing values, beyond which a case would be excluded from the index calculation.

[MarHai]

I am unsure how such an argument/parameter would look like. A threshold number of x out of y variables that can (not) be NA?