This function splits up the initial data set into multiple sets based on their value for id_field. For example, if we have a data set with a field named id that has values ranging from 11 to 15, calling av_state <- group_by('id') will set av_state$data to a list of five items. This list is ordered by the value of the id field. Then, we can use av_state$data[[1]] (or equivalently, av_state$data[['11']]) to retrieve the rows in the data set that have id 11. Likewise, use av_state$data[[2]] or av_state\$data[['12']] for rows with id 12. This function can only be called once per av_state.

group_by(av_state, id_field)

## Arguments

av_state an object of class av_state the name of a column in the data set

## Value

This function returns the modified av_state object.

## Examples

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