This series of vignettes in the Gallery section aim to
demonstrate the functionality of eider through examples
that are similar to real-life usage. To do this, we have created a
series of randomly generated datasets that are stored with the package.
You can access these datasets using the eider_example()
function, which will return the path to where the dataset is stored in
your installation of R.
pis_data_filepath <- eider_example("random_pis_data.csv")
pis_data_filepath
#> [1] "/tmp/RtmpqoMDH9/Rinstb692df9905c/eider/extdata/random_pis_data.csv"In this specific vignette, we are using simulated Prescribing
Information System (PIS). Our dataset does not contain every column
specified in here, but serves as a useful example of how real-life data
may be treated using eider.
pis_data <- utils::read.csv(pis_data_filepath) %>%
dplyr::mutate(paid_date = lubridate::ymd(paid_date))
dplyr::glimpse(pis_data)
#> Rows: 100
#> Columns: 4
#> $ id <int> 19, 19, 19, 7, 3, 18, 2, 5, 2, 6, 10, 2, 15, 4, 15, 6, 15,…
#> $ paid_date <date> 2017-12-15, 2016-08-11, 2015-07-07, 2017-03-14, 2015-08-0…
#> $ bnf_section <int> 113, 106, 105, 112, 111, 106, 108, 104, 109, 110, 109, 115…
#> $ num_items <int> 3, 5, 1, 1, 1, 3, 4, 3, 1, 4, 4, 5, 3, 5, 1, 2, 4, 2, 3, 1…(Note that when the data is loaded by eider, the date
columns are automatically converted to the date type for you: you do not
need to do the manual processing above.)
This simplified table has 4 columns:
id, which is a numeric patient ID;paid_date, which is the date the prescription was paid
for;bnf_section, which is a code for the type of drug
prescribed;num_items, which is the number of items
prescribed.A simple example of a feature here is the number of unique
prescription type each patient has received, which corresponds to the
number of distinct values of bnf_section per
id.
The JSON required uses the nunique transformation type,
and we must specify the column over which we want to take the distinct
values using "aggregation_column": "bnf_section".
unique_bnf_filepath <- eider_example("distinct_bnf_prescriptions.json")
writeLines(readLines(unique_bnf_filepath))
#> {
#> "source_table": "pis",
#> "transformation_type": "nunique",
#> "grouping_column": "id",
#> "absent_default_value": 0,
#> "aggregation_column": "bnf_section",
#> "output_feature_name": "unique_bnf_sections"
#> }res <- run_pipeline(
data_sources = list(pis = pis_data_filepath),
feature_filenames = unique_bnf_filepath
)
dplyr::glimpse(res$features)
#> Rows: 20
#> Columns: 2
#> $ id <int> 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, …
#> $ unique_bnf_sections <int> 3, 3, 4, 6, 2, 5, 3, 2, 5, 2, 4, 1, 4, 4, 3, 6, 3,…A slightly more complicated example involves summing up the total
number of items prescribed, but only counting those transactions since
2016—in other words, those where the paid_date is on or
after 1 January 2016.
To do this, we perform a sum over the
num_items column, and use a filter to remove any rows that
are prior to this date. The filter has the type
"date_gt_eq", which means greater than or equal to.
drugs_since_2016_filepath <- eider_example("num_prescriptions_since_2016.json")
writeLines(readLines(drugs_since_2016_filepath))
#> {
#> "source_table": "pis",
#> "transformation_type": "sum",
#> "grouping_column": "id",
#> "absent_default_value": 0,
#> "aggregation_column": "num_items",
#> "output_feature_name": "num_prescriptions_since_2016",
#> "filter": {
#> "column": "paid_date",
#> "type": "date_gt_eq",
#> "value": "2016-01-01"
#> }
#> }res <- run_pipeline(
data_sources = list(pis = pis_data_filepath),
feature_filenames = drugs_since_2016_filepath
)
dplyr::glimpse(res$features)
#> Rows: 20
#> Columns: 2
#> $ id <int> 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,…
#> $ num_prescriptions_since_2016 <int> 10, 5, 19, 21, 5, 8, 12, 6, 8, 3, 4, 6, 7…As a warm-up to feature 4, we will write a small feature that looks
up the maximum value of num_items for each patient in the
table. This is a max transformation type, which is very
similar to the nunique and sum that we have
seen above, except that we run a different aggregation function on the
num_items column: instead of counting the unique values or
summing them, we pick out the maximum value.
max_items_filepath <- eider_example("max_drugs_in_transaction.json")
writeLines(readLines(max_items_filepath))
#> {
#> "source_table": "pis",
#> "transformation_type": "max",
#> "grouping_column": "id",
#> "absent_default_value": 0,
#> "aggregation_column": "num_items",
#> "output_feature_name": "max_drugs_in_transaction"
#> }res <- run_pipeline(
data_sources = list(pis = pis_data_filepath),
feature_filenames = max_items_filepath
)
dplyr::glimpse(res$features)
#> Rows: 20
#> Columns: 2
#> $ id <int> 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,…
#> $ max_drugs_in_transaction <int> 4, 3, 5, 7, 5, 4, 4, 4, 6, 4, 5, 6, 3, 4, 3, …Now, consider a slightly more complicated request: what is the
largest number of items that were prescribed to a patient in a
single day? Clearly, this is also a max transformation
type, but we need to now somehow group together any rows that belong to
the same patient and the same date, and add up those values.
To do this, we can use eider’s preprocessing
functionality, which is described more thoroughly in the preprocessing vignette. Specifically,
we can:
id and paid_date
columns;num_items column with
the sum of those values.In JSON, these instructions can be specified using the
"preprocessing" key:
The full JSON file is the same as in Feature 3, but just with this preprocessing block added in:
max_items_day_filepath <- eider_example("max_drugs_in_day.json")
writeLines(readLines(max_items_day_filepath))
#> {
#> "source_table": "pis",
#> "transformation_type": "max",
#> "grouping_column": "id",
#> "absent_default_value": 0,
#> "aggregation_column": "num_items",
#> "preprocess": {
#> "on": [
#> "id",
#> "paid_date"
#> ],
#> "replace_with_sum": "num_items"
#> },
#> "output_feature_name": "max_drugs_in_day"
#> }res <- run_pipeline(
data_sources = list(pis = pis_data_filepath),
feature_filenames = c(max_items_filepath, max_items_day_filepath)
)
dplyr::glimpse(res$features)
#> Rows: 20
#> Columns: 3
#> $ id <int> 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,…
#> $ max_drugs_in_transaction <int> 4, 3, 5, 7, 5, 4, 4, 4, 6, 4, 5, 6, 3, 4, 3, …
#> $ max_drugs_in_day <int> 4, 3, 8, 7, 5, 6, 8, 4, 6, 4, 5, 6, 3, 4, 3, …Notice the differences between the two feature columns above: in the
second (max_drugs_in_day) we have successfully aggregated
transactions which happened on the same day, and thus the values (where
they differ) are larger.