dd_duration: Calculate Prescription Durations
In amarshall1/prescribeR: Quantify Exposure Based On Routine Prescribing Data

Description Usage Arguments Value Examples

Calculates the duration in days of individual prescriptions based on the number of daily doses dispensed. A multiplication factor is applied to allow for use in cases where, for example an assumption of less or more than 1 DDD per day is required

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dd_duration(df, drug, dd_factor = 1, patient_id_col = "patient_id",
  drug_id_col = "drug_id", presc_date_col = "presc_date_x",
  dd_disp_col = "dd_disp", date_format)

`df`	a data frame containing prescribing records to be analysed - records must contain at least a paitent ID, drug ID, a prescription date
`drug`	a string containing a drug ID to be used to limit the prescribing data to the drug(s) of interest, accepts regular expressions
`dd_factor`	a number, a multiplication factor applied to the dd_disp field to calculate prescription duration
`patient_id_col`	a string, the name of the column in `df` containing the patient IDs
`drug_id_col`	a string, the name of the column in `df` containing the drug IDs
`presc_date_col`	a string, the name of the column in `df` containing the prescption date
`dd_disp_col`	a string, the name of the column in `df` containing the number of daily doses dispensed
`date_format`	a string, the format of the dates in `df`

a modified version of df with records for the drug of interest with the duration field added

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dd_duration(synth_presc, drug = "212000",
drug_id_col = "bnf_paragraph", presc_date_col = "presc_date",
dd_disp_col = "ddd_dispensed", date_format = "%Y-%m-%d")