To see the available diseasystores on your system, you
can use the available_diseasystores() function.
This function looks for diseasystores on the current
search path. By default, this will show the diseasystores
bundled with the base package. If you have extended
diseasystore with either your own
diseasystores or from an external package, then attaching
the package to your search path will allow it to show up as
available.
Note: diseasystores are found if they are defined within
packages named diseasystore* and are of the class
DiseasystoreBase.
Each of these diseasystores may have their own vignette
that further details their content, use and/or tips and tricks. This is
for example the case with DiseasystoreGoogleCovid19.
To use a diseasystore we need to first do some
configuration. The diseasystores are designed to work with
data bases to store the computed features in. Each
diseasystore may require individual configuration as listed
in its documentation or accompanying vignette.
For this Quick start, we will configure a
DiseasystoreGoogleCovid19 to use a local
SQLite data base Ideally, we want to use a faster, more
capable, data base to store the features in. The
diseasystores uses SCDB in the back end and
can use any data base back end supported by SCDB.
ds <- DiseasystoreGoogleCovid19$new(
target_conn = DBI::dbConnect(RSQLite::SQLite()),
start_date = as.Date("2020-03-01"),
end_date = as.Date("2020-03-15")
)When we create our new diseasystore instance, we also
supply start_date and end_date arguments.
These are not strictly required, but make getting features for this time
interval simpler.
Once configured we can query the available features in the
diseasystore
These features can be retrieved individually (using the
start_date and end_date we specified during
creation of ds):
Notice that features have associated “key_*” and “valid_from/until”
columns. These are used for one of the primary selling points of
diseasystore, namely automatic aggregation.
Go get features for other time intervals, we can manually supply
start_date and/or end_date:
The diseasystore automatically expands the computed
features.
Say a given “n_hospital” has been computed between 2020-03-01 and
2020-03-15. In this case, the call
$get_feature("n_hospital", start_date = as.Date("2020-03-01"), end_date = as.Date("2020-03-20")
only needs to compute the feature between 2020-03-16 and 2020-03-20.
Through using {SCDB} as the back end, the features are
stored even as new data becomes available. This way, we get a
time-versioned record of the features provided by
diseasystore.
The features being computed is controlled through the
slice_ts argument. By default, diseasystores
uses today’s date for this argument.
The dynamical expansion of the features described above is only valid
for any given slice_ts. That is, if a feature has been
computed for a time interval on one slice_ts,
diseasystore will recompute the feature for any other
slice_ts.
This way, feature computation can be implemented into continuous integration (requesting features will preserve a history of computed features). Furthermore, post-hoc analysis can be performed by computing features as they would have looked on previous dates.
The real strength of diseasystore comes from its
built-in automatic aggregation.
We saw above that the features come with additional associated “key_*” and “valid_from/until” columns.
This additional information is used to do automatic aggregation
through the $key_join_features() method (see extending-diseasystore for more
details).
To use this method, you need to provide the observable
that you want to aggregate and the stratification you want
to apply to the aggregation.
Lets start with an simple example where we request no stratification
(NULL):
This gives us the same feature information as
ds$get_feature("n_hospital") but simplified to give the
observable per day (in this case, the number of people
hospitalised).
To specify a level of stratification, we need to supply
a list of quosures (see
help("topic-quosure", package = "rlang")).
The stratification argument is very flexible, so we can
supply any valid R expression:
Sometimes, it is need to clear the compute features from the data
base. For this purpose, we provide the drop_diseasystore()
function.
By default, this deletes all stored features in the default
diseasystore schema. A pattern argument to
match tables by and a schema argument to specify the schema
to delete from1.
diseasystores have a number of options available to make
configuration easier. These options all start with “diseasystore.”.
options()[purrr::keep(names(options()), ~ startsWith(., "diseasystore"))]
#> $diseasystore.DiseasystoreEcdcRespiratoryViruses.pull
#> [1] TRUE
#>
#> $diseasystore.DiseasystoreEcdcRespiratoryViruses.remote_conn
#> [1] "https://api.github.com/repos/EU-ECDC/Respiratory_viruses_weekly_data"
#>
#> $diseasystore.DiseasystoreEcdcRespiratoryViruses.source_conn
#> [1] "https://api.github.com/repos/EU-ECDC/Respiratory_viruses_weekly_data"
#>
#> $diseasystore.DiseasystoreEcdcRespiratoryViruses.target_conn
#> [1] ""
#>
#> $diseasystore.DiseasystoreEcdcRespiratoryViruses.target_schema
#> [1] ""
#>
#> $diseasystore.DiseasystoreGoogleCovid19.n_max
#> [1] 1000
#>
#> $diseasystore.DiseasystoreGoogleCovid19.remote_conn
#> [1] "https://storage.googleapis.com/covid19-open-data/v3/"
#>
#> $diseasystore.DiseasystoreGoogleCovid19.source_conn
#> [1] "https://storage.googleapis.com/covid19-open-data/v3/"
#>
#> $diseasystore.DiseasystoreGoogleCovid19.target_conn
#> [1] ""
#>
#> $diseasystore.DiseasystoreGoogleCovid19.target_schema
#> [1] ""
#>
#> $diseasystore.lock_wait_increment
#> [1] 15
#>
#> $diseasystore.lock_wait_max
#> [1] 1800
#>
#> $diseasystore.source_conn
#> [1] ""
#>
#> $diseasystore.target_conn
#> [1] ""
#>
#> $diseasystore.target_schema
#> [1] "ds"
#>
#> $diseasystore.verbose
#> [1] FALSENotice that several options are set as empty strings (““). These are
treated as NULL by diseasystore2.
Importantly, the options are scoped. Consider the above
options for “source_conn”: Looking at the list of options we find
“diseasystore.source_conn” and
“diseasystore.DiseasystoreGoogleCovid19.source_conn”. The former is a
general setting while the latter is specific setting for
DiseasystoreGoogleCovid19. The general setting is used as
fallback if no specific setting is found.
This allows you to set a general configuration to use and to overwrite it for specific cases.
To get the option related to a scope, we can use the
diseasyoption() function.
diseasyoption("source_conn", class = "DiseasystoreGoogleCovid19")
#> [1] "https://storage.googleapis.com/covid19-open-data/v3/"As we saw in the options, a source_conn option was
defined specifically for DiseasystoreGoogleCovid19.
If we try the same for the hypothetical
DiseasystoreDiseaseY, we see that no value is defined as we
have not yet configured the fallback value.
If we change our general setting for source_conn and
retry, we see that we get the fallback value.
options("diseasystore.source_conn" = file.path("local", "path"))
diseasyoption("source_conn", class = "DiseasystoreDiseaseY")
#> [1] "local/path"Finally, we can use the .default argument as a final
fallback value in case no option is set for either general or specific
case.