# Concatenating cohort records

    library(CohortConstructor)
    library(CohortCharacteristics)
    library(ggplot2)

For this example we’ll use the Eunomia synthetic data from the CDMConnector package.

    con <- DBI::dbConnect(duckdb::duckdb(), dbdir = eunomiaDir())
    cdm <- CDMConnector::cdmFromCon(con, cdmSchema = "main",
                        writeSchema = "main", writePrefix = "my_study_")

Let’s start by creating a cohort of users of acetaminophen

    cdm$medications <- conceptCohort(cdm = cdm,
                                     conceptSet = list("acetaminophen" = 1127433),
                                     name = "medications")
    cohortCount(cdm$medications)

We can merge cohort records using the `collapseCohorts()` function in the CohortConstructor package. The function allows us to specifying the number of days between two cohort entries, which will then be merged into a single record.

Let’s first define a new cohort where records within 1095 days (~ 3 years) of each other will be merged.

    cdm$medications_collapsed <- cdm$medications |>
      collapseCohorts(
      gap = 1095,
      name = "medications_collapsed"
    )

Let’s compare how this function would change the records of a single individual.

    cdm$medications |>
      filter(subject_id == 1)
    cdm$medications_collapsed |>
      filter(subject_id == 1)

Subject 1 initially had 4 records between 1971 and 1982. After specifying that records within three years of each other are to be merged, the number of records decreases to three. The record from 1980-03-15 to 1980-03-29 and the record from 1982-09-11 to 1982-10-02 are merged to create a new record from 1980-03-15 to 1982-10-02.

Now let’s look at how the cohorts have been changed.

    summary_attrition <- summariseCohortAttrition(cdm$medications_collapsed)
    tableCohortAttrition(summary_attrition)