observatory-extension/docs/reference/06-discovery-functions.md

Discovery Functions

If you are using the [discovery methods]({{ site.dataobservatory_docs}}/guides/overview/#discovery-methods) from the Data Observatory, use the following functions to retrieve [boundary]({{ site.dataobservatory_docs}}/guides/overview/#boundary-data) and [measures]({{ site.dataobservatory_docs}}/guides/overview/#measures-data) data.

OBS_Search(search_term)

Use arbitrary text to search all available measures

Arguments

Name	Description
search_term	a string to search for available measures
boundary_id	a string identifier for a boundary geometry (optional)

Returns

A TABLE containing the following properties

Key	Description
id	the unique id of the measure for use with the OBS_GetMeasure function
name	the human readable name of the measure
description	a brief description of the measure
aggregate	sum are raw count values, median are statistical medians, average are statistical averages, undefined other (e.g. an index value)
source	where the data came from (e.g. US Census Bureau)

Example

SELECT * FROM OBS_Search('home value')

OBS_GetAvailableBoundaries(point_geometry)

Returns available boundary_ids at a given point geometry.

Arguments

Name	Description
point_geometry	a WGS84 point geometry (e.g. the_geom)

Returns

A TABLE containing the following properties

Key	Description
boundary_id	a boundary identifier from the [Boundary ID Glossary]({{ site.dataobservatory_docs}}/guides/glossary/#boundary-ids)
description	a brief description of the boundary dataset
time_span	the timespan attached the boundary. this does not mean that the boundary is invalid outside of the timespan, but is the explicit timespan published with the geometry.

Example

SELECT * FROM OBS_GetAvailableBoundaries(CDB_LatLng(40.7, -73.9))

OBS_GetAvailableNumerators(bounds, filter_tags, denom_id, geom_id, timespan)

Return available numerators within a boundary and with the specified filter_tags.

Arguments

Name	Type	Description
bounds	Geometry(Geometry, 4326)	a geometry which some of the numerator's data must intersect with
filter_tags	Text[]	a list of filters. Only numerators for which all of these apply are returned NULL to ignore (optional)
denom_id	Text	the ID of a denominator to check whether the numerator is valid against. Will not reduce length of returned table, but will change values for valid_denom (optional)
geom_id	Text	the ID of a geometry to check whether the numerator is valid against. Will not reduce length of returned table, but will change values for valid_geom (optional)
timespan	Text	the ID of a timespan to check whether the numerator is valid against. Will not reduce length of returned table, but will change values for valid_timespan (optional)

Returns

A TABLE containing the following properties

Key	Type	Description
numer_id	Text	The ID of the numerator
numer_name	Text	A human readable name for the numerator
numer_description	Text	Description of the numerator. Is sometimes NULL
numer_weight	Numeric	Numeric "weight" of the numerator. Ignored.
numer_license	Text	ID of the license for the numerator
numer_source	Text	ID of the source for the numerator
numer_type	Text	Postgres type of the numerator
numer_aggregate	Text	Aggregate type of the numerator. If 'SUM', this can be normalized by area
numer_extra	JSONB	Extra information about the numerator column. Ignored.
numer_tags	Text[]	Array of all tags applying to this numerator
valid_denom	Boolean	True if the denom_id argument is a valid denominator for this numerator, False otherwise
valid_geom	Boolean	True if the geom_id argument is a valid geometry for this numerator, False otherwise
valid_timespan	Boolean	True if the timespan argument is a valid timespan for this numerator, False otherwise

Examples

Obtain all numerators that are available within a small rectangle.

SELECT * FROM OBS_GetAvailableNumerators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326))

Obtain all numerators that are available within a small rectangle and are for the United States only.

SELECT * FROM OBS_GetAvailableNumerators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), '{section/tags.united_states}');

Obtain all numerators that are available within a small rectangle and are employment related for the United States only.

SELECT * FROM OBS_GetAvailableNumerators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), '{section/tags.united_states, subsection/tags.employment}');

Obtain all numerators that are available within a small rectangle and are related to both employment and age & gender for the United States only.

SELECT * FROM OBS_GetAvailableNumerators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), '{section/tags.united_states, subsection/tags.employment, subsection/tags.age_gender}');

Obtain all numerators that work with US population (us.census.acs.B01003001) as a denominator.

SELECT * FROM OBS_GetAvailableNumerators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, 'us.census.acs.B01003001')
WHERE valid_denom IS True;

Obtain all numerators that work with US states (us.census.tiger.state) as a geometry.

SELECT * FROM OBS_GetAvailableNumerators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, NULL, 'us.census.tiger.state')
WHERE valid_geom IS True;

Obtain all numerators available in the timespan 2011 - 2015.

SELECT * FROM OBS_GetAvailableNumerators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, NULL, NULL, '2011 - 2015')
WHERE valid_timespan IS True;

OBS_GetAvailableDenominators(bounds, filter_tags, numer_id, geom_id, timespan)

Return available denominators within a boundary and with the specified filter_tags.

Arguments

Name	Type	Description
bounds	Geometry(Geometry, 4326)	a geometry which some of the denominator's data must intersect with
filter_tags	Text[]	a list of filters. Only denominators for which all of these apply are returned NULL to ignore (optional)
numer_id	Text	the ID of a numerator to check whether the denominator is valid against. Will not reduce length of returned table, but will change values for valid_numer (optional)
geom_id	Text	the ID of a geometry to check whether the denominator is valid against. Will not reduce length of returned table, but will change values for valid_geom (optional)
timespan	Text	the ID of a timespan to check whether the denominator is valid against. Will not reduce length of returned table, but will change values for valid_timespan (optional)

Returns

A TABLE containing the following properties

Key	Type	Description
denom_id	Text	The ID of the denominator
denom_name	Text	A human readable name for the denominator
denom_description	Text	Description of the denominator. Is sometimes NULL
denom_weight	Numeric	Numeric "weight" of the denominator. Ignored.
denom_license	Text	ID of the license for the denominator
denom_source	Text	ID of the source for the denominator
denom_type	Text	Postgres type of the denominator
denom_aggregate	Text	Aggregate type of the denominator. If 'SUM', this can be normalized by area
denom_extra	JSONB	Extra information about the denominator column. Ignored.
denom_tags	Text[]	Array of all tags applying to this denominator
valid_numer	Boolean	True if the numer_id argument is a valid numerator for this denominator, False otherwise
valid_geom	Boolean	True if the geom_id argument is a valid geometry for this denominator, False otherwise
valid_timespan	Boolean	True if the timespan argument is a valid timespan for this denominator, False otherwise

Examples

Obtain all denominators that are available within a small rectangle.

SELECT * FROM OBS_GetAvailableDenominators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326));

Obtain all denominators that are available within a small rectangle and are for the United States only.

SELECT * FROM OBS_GetAvailableDenominators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), '{section/tags.united_states}');

Obtain all denominators for male population (us.census.acs.B01001002).

SELECT * FROM OBS_GetAvailableDenominators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, 'us.census.acs.B01001002')
WHERE valid_numer IS True;

Obtain all denominators that work with US states (us.census.tiger.state) as a geometry.

SELECT * FROM OBS_GetAvailableDenominators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, NULL, 'us.census.tiger.state')
WHERE valid_geom IS True;

Obtain all denominators available in the timespan 2011 - 2015.

SELECT * FROM OBS_GetAvailableDenominators(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, NULL, NULL, '2011 - 2015')
WHERE valid_timespan IS True;

OBS_GetAvailableGeometries(bounds, filter_tags, numer_id, denom_id, timespan, number_geometries)

Return available geometries within a boundary and with the specified filter_tags.

Arguments

Name	Type	Description
bounds	Geometry(Geometry, 4326)	a geometry which must intersect the geometry
filter_tags	Text[]	a list of filters. Only geometries for which all of these apply are returned NULL to ignore (optional)
numer_id	Text	the ID of a numerator to check whether the geometry is valid against. Will not reduce length of returned table, but will change values for valid_numer (optional)
denom_id	Text	the ID of a denominator to check whether the geometry is valid against. Will not reduce length of returned table, but will change values for valid_denom (optional)
timespan	Text	the ID of a timespan to check whether the geometry is valid against. Will not reduce length of returned table, but will change values for valid_timespan (optional)
number_geometries	Integer	an additional variable that is used to adjust the calculation of the [score]({{ site.dataobservatory_docs}}/guides/discovery-functions/#returns-4) (optional)

Returns

A TABLE containing the following properties

Key	Type	Description
geom_id	Text	The ID of the geometry
geom_name	Text	A human readable name for the geometry
geom_description	Text	Description of the geometry. Is sometimes NULL
geom_weight	Numeric	Numeric "weight" of the geometry. Ignored.
geom_aggregate	Text	Aggregate type of the geometry. Ignored.
geom_license	Text	ID of the license for the geometry
geom_source	Text	ID of the source for the geometry
geom_type	Text	Postgres type of the geometry
geom_extra	JSONB	Extra information about the geometry column. Ignored.
geom_tags	Text[]	Array of all tags applying to this geometry
valid_numer	Boolean	True if the numer_id argument is a valid numerator for this geometry, False otherwise
valid_denom	Boolean	True if the geom_id argument is a valid geometry for this geometry, False otherwise
valid_timespan	Boolean	True if the timespan argument is a valid timespan for this geometry, False otherwise
score	Numeric	Score between 0 and 100 for this geometry, higher numbers mean that this geometry is a better choice for the passed extent
numtiles	Numeric	How many raster tiles were read for score, numgeoms, and percentfill estimates
numgeoms	Numeric	About how many of these geometries fit inside the passed extent
percentfill	Numeric	About what percentage of the passed extent is filled with these geometries
estnumgeoms	Numeric	Ignored
meanmediansize	Numeric	Ignored

Examples

Obtain all geometries that are available within a small rectangle.

SELECT * FROM OBS_GetAvailableGeometries(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326));

Obtain all geometries that are available within a small rectangle and are for the United States only.

SELECT * FROM OBS_GetAvailableGeometries(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), '{section/tags.united_states}');

Obtain all geometries that work with total population (us.census.acs.B01003001).

SELECT * FROM OBS_GetAvailableGeometries(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, 'us.census.acs.B01003001')
WHERE valid_numer IS True;

Obtain all geometries with timespan 2015.

SELECT * FROM OBS_GetAvailableGeometries(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, NULL, NULL, '2015')
WHERE valid_timespan IS True;

OBS_GetAvailableTimespans(bounds, filter_tags, numer_id, denom_id, geom_id)

Return available timespans within a boundary and with the specified filter_tags.

Arguments

Name	Type	Description
bounds	Geometry(Geometry, 4326)	a geometry which some of the timespan's data must intersect with
filter_tags	Text[]	a list of filters. Ignore
numer_id	Text	the ID of a numerator to check whether the timespans is valid against. Will not reduce length of returned table, but will change values for valid_numer (optional)
denom_id	Text	the ID of a denominator to check whether the timespans is valid against. Will not reduce length of returned table, but will change values for valid_denom (optional)
geom_id	Text	the ID of a geometry to check whether the timespans is valid against. Will not reduce length of returned table, but will change values for valid_geom (optional)

Returns

A TABLE containing the following properties

Key	Type	Description
timespan_id	Text	The ID of the timespan
timespan_name	Text	A human readable name for the timespan
timespan_description	Text	Ignored
timespan_weight	Numeric	Ignored
timespan_aggregate	Text	Ignored
timespan_license	Text	Ignored
timespan_source	Text	Ignored
timespan_type	Text	Ignored
timespan_extra	JSONB	Ignored
timespan_tags	JSONB	Ignored
valid_numer	Boolean	True if the numer_id argument is a valid numerator for this timespan, False otherwise
valid_denom	Boolean	True if the timespan argument is a valid timespan for this timespan, False otherwise
valid_geom	Boolean	True if the geom_id argument is a valid geometry for this timespan, False otherwise

Examples

Obtain all timespans that are available within a small rectangle.

SELECT * FROM OBS_GetAvailableTimespans(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326));

Obtain all timespans for total population (us.census.acs.B01003001).

SELECT * FROM OBS_GetAvailableTimespans(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, 'us.census.acs.B01003001')
WHERE valid_numer IS True;

Obtain all timespans that work with US states (us.census.tiger.state) as a geometry.

SELECT * FROM OBS_GetAvailableTimespans(
  ST_MakeEnvelope(-74, 41, -73, 40, 4326), NULL, NULL, NULL, 'us.census.tiger.state')
WHERE valid_geom IS True;