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Update the dataset definition

You've successfully generated a dataset from the code in your study, but at the moment it only contains one data column.

Now we'll add some code to create an extra column.

Add an age column🔗

  1. The "Explorer" on the left hand side lists the files and folders in your research repository. Find and click on the dataset_definition.py file inside the analysis folder. This file contains a dataset definition, specifying the population that you'd like to study (dataset rows) and what you need to know about them (dataset columns). It is written in ehrQL.
  2. Add some text so that the file looks like this (new text highlighted): 
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    from ehrql import create_dataset
from ehrql.tables.tpp import patients, practice_registrations

dataset = create_dataset()

index_date = "2020-03-31"

has_registration = practice_registrations.for_patient_on(
    index_date
).exists_for_patient()

dataset.define_population(has_registration)

dataset.sex = patients.sex
dataset.age = patients.age_on(index_date)
    Lines 8-12 mean "I'm interested in all patients who were registered at a practice on the index date"; line 14 "Give me a column of data corresponding to the sex of each patient"; and line 15 "Give me a column of data corresponding to the age of each patient on the given date".
  3. If you type the following into your terminal:
opensafely exec ehrql:v1 generate-dataset analysis/dataset_definition.py

and press Enter, you will see a new randomly generated dataset which now contains the additional age column.