18 KiB
Measures Functions
Data Observatory Measures are the numerical location data you can access. The measure functions allow you to access individual measures to augment your own data or integrate in your analysis workflows. Measures are used by sending an identifier or a geometry (point or polygon) and receiving back a measure (an absolute value) for that location.
There are hundreds of measures and the list is growing with each release. You can currently discover and learn about measures contained in the Data Observatory by downloading our Data Catalog.
You can access measures through CARTO Builder. The same methods will work if you are using the CARTO Engine to develop your application. We encourage you to use table modifying methods (UPDATE and INSERT) over dynamic methods (SELECT).
OBS_GetUSCensusMeasure(point geometry, measure_name text)
The OBS_GetUSCensusMeasure(point, measure_name) function returns a measure based on a subset of the US Census variables at a point location. The OBS_GetUSCensusMeasure function is limited to only a subset of all measures that are available in the Data Observatory, to access the full list, use measure IDs with the OBS_GetMeasure function below.
Arguments
| Name | Description |
|---|---|
| point | a WGS84 point geometry (the_geom) |
| measure_name | a human readable name of a US Census variable. The list of measure_names is available in the Glossary. |
| normalize | for measures that are are sums (e.g. population) the default normalization is 'area' and response comes back as a rate per square kilometer. Other options are 'denominator', which will use the denominator specified in the Data Catalog (optional) |
| boundary_id | source of geometries to pull measure from (e.g., 'us.census.tiger.census_tract') |
| time_span | time span of interest (e.g., 2010 - 2014) |
Returns
A NUMERIC value
| Key | Description |
|---|---|
| value | the raw or normalized measure |
Example
Add a measure to an empty numeric column based on point locations in your table.
UPDATE tablename
SET total_population = OBS_GetUSCensusMeasure(the_geom, 'Total Population')
OBS_GetUSCensusMeasure(polygon geometry, measure_name text)
The OBS_GetUSCensusMeasure(point, measure_name) function returns a measure based on a subset of the US Census variables within a given polygon. The OBS_GetUSCensusMeasure function is limited to only a subset of all measures that are available in the Data Observatory, to access the full list, use the OBS_GetUSCensusMeasure function below.
Arguments
| Name | Description |
|---|---|
| polygon | a WGS84 polygon geometry (the_geom) |
| measure_name | a human readable string name of a US Census variable. The list of measure_names is available in the Glossary. |
| normalize | for measures that are sums (e.g. population) the default normalization is 'none' and response comes back as a raw value. Other options are 'denominator', which will use the denominator specified in the Data Catalog (optional) |
| boundary_id | source of geometries to pull measure from (e.g., 'us.census.tiger.census_tract') |
| time_span | time span of interest (e.g., 2010 - 2014) |
Returns
A NUMERIC value
| Key | Description |
|---|---|
| value | the raw or normalized measure |
Example
Add a measure to an empty numeric column based on polygons in your table
UPDATE tablename
SET local_male_population = OBS_GetUSCensusMeasure(the_geom, 'Male Population')
OBS_GetMeasure(point geometry, measure_id text)
The OBS_GetMeasure(point, measure_id) function returns any Data Observatory measure at a point location. You can browse all available Measures in the Catalog.
Arguments
| Name | Description |
|---|---|
| point | a WGS84 point geometry (the_geom) |
| measure_id | a measure identifier from the Data Observatory (see available measures). It is important to note that these are different than 'measure_name' used in the Census based functions above. |
| normalize | for measures that are are sums (e.g. population) the default normalization is 'area' and response comes back as a rate per square kilometer. The other option is 'denominator', which will use the denominator specified in the Data Catalog. (optional) |
| boundary_id | source of geometries to pull measure from (e.g., 'us.census.tiger.census_tract') |
| time_span | time span of interest (e.g., 2010 - 2014) |
Returns
A NUMERIC value
| Key | Description |
|---|---|
| value | the raw or normalized measure |
Example
Add a measure to an empty numeric column based on point locations in your table
UPDATE tablename
SET median_home_value_sqft = OBS_GetMeasure(the_geom, 'us.zillow.AllHomes_MedianValuePerSqft')
OBS_GetMeasure(polygon geometry, measure_id text)
The OBS_GetMeasure(polygon, measure_id) function returns any Data Observatory measure calculated within a polygon.
Arguments
| Name | Description |
|---|---|
| polygon_geometry | a WGS84 polygon geometry (the_geom) |
| measure_id | a measure identifier from the Data Observatory (see available measures) |
| normalize | for measures that are are sums (e.g. population) the default normalization is 'none' and response comes back as a raw value. Other options are 'denominator', which will use the denominator specified in the Data Catalog (optional) |
| boundary_id | source of geometries to pull measure from (e.g., 'us.census.tiger.census_tract') |
| time_span | time span of interest (e.g., 2010 - 2014) |
Returns
A NUMERIC value
| Key | Description |
|---|---|
| value | the raw or normalized measure |
Example
Add a measure to an empty column based on polygons in your table
UPDATE tablename
SET household_count = OBS_GetMeasure(the_geom, 'us.census.acs.B11001001')
Errors
- If an unrecognized normalization type is input, raise an error:
'Only valid inputs for "normalize" are "area" (default) and "denominator".
OBS_GetMeasureById(geom_ref text, measure_id text, boundary_id text)
The OBS_GetMeasureById(geom_ref, measure_id, boundary_id) function returns any Data Observatory measure that corresponds to the boundary in boundary_id that has a geometry reference of geom_ref.
Arguments
| Name | Description |
|---|---|
| geom_ref | a geometry reference (e.g., a US Census geoid) |
| measure_id | a measure identifier from the Data Observatory (see available measures) |
| boundary_id | source of geometries to pull measure from (e.g., 'us.census.tiger.census_tract') |
| time_span (optional) | time span of interest (e.g., 2010 - 2014). If NULL is passed, the measure from the most recent data will be used. |
Returns
A NUMERIC value
| Key | Description |
|---|---|
| value | the raw measure associated with geom_ref |
Example
Add a measure to an empty column based on county geoids in your table
UPDATE tablename
SET household_count = OBS_GetMeasureById(geoid_column, 'us.census.acs.B11001001', 'us.census.tiger.county')
Errors
- Returns
NULLif there is a mismatch between the geometry reference and the boundary id such as using the geoid of a county with the boundary of block groups
OBS_GetCategory(point geometry, category_id text)
The OBS_GetCategory(point, category_id) function returns any Data Observatory Category value at a point location. The Categories available are currently limited to Segmentation categories. See the Segmentation section of the Catalog for more detail.
Arguments
| Name | Description |
|---|---|
| point | a WGS84 point geometry (the_geom) |
| category_id | a category identifier from the Data Observatory (see available measures). |
Returns
A TEXT value
| Key | Description |
|---|---|
| value | a text based category found at the supplied point |
Example
Add the Category to an empty column text column based on point locations in your table
UPDATE tablename
SET segmentation = OBS_GetCategory(the_geom, 'us.census.spielman_singleton_segments.X55')
OBS_GetMeta(extent geometry, metadata json)
The OBS_GetMeta(extent, metadata) function returns a completed Data
Observatory metadata JSON Object for use in OBS_GetData(geomvals, metadata) or OBS_GetData(ids, metadata). It is not possible to pass
metadata to those functions if it is not processed by OBS_GetMeta(extent, metadata) first.
Arguments
| Name | Description |
|---|---|
| extent | A geometry of the extent of the input geometries |
| metadata | A JSON array composed of metadata input objects. Each indicates one desired measured for an output column, and optionally additional parameters about that column |
The schema of the metadata input objects are as follows:
| Metadata Input Key | Description |
|---|---|
| numer_id | The identifier for the desired measurement. If left blank, but a geom_id is specified, the column will return a geometry instead of a measurement. |
| geom_id | Identifier for a desired geographic boundary level to use when calculating measures. Will be automatically assigned if undefined. If defined but numer_id is blank, then the column will return a geometry instead of a measurement. |
| normalization | The desired normalization. One of 'area', 'prenormalized', or 'denominated'. 'Area' will normalize the measure per square kilometer, 'prenormalized' will return the original value, and 'denominated' will normalize by a denominator. Ignored if this metadata object specifies a geometry. |
| denom_id | Identifier for a desired normalization column in case normalization is 'denominated'. Will be automatically assigned if necessary. Ignored if this metadata object specifies a geometry. |
| numer_timespan | The desired timespan for the measurement. Defaults to most recent timespan available if left unspecified. |
| geom_timespan | The desired timespan for the geometry. Defaults to most recent timespan available if left unspecified. |
Returns
A JSON array composed of metadata output objects.
| Key | Description |
|---|---|
| meta | A JSON array with completed metadata for the requested data, including all keys below |
The schema of the metadata output objects are as follows. You should pass this
array as-is to OBS_GetData. If you modify any values the function will
fail.
| Metadata Output Key | Description |
|---|---|
| numer_id | Identifier for desired measurement. |
| numer_timespan | Timespan that will be used of the desired measurement. |
| numer_name | Human-readable name of desired measure |
| numer_type | PostgreSQL/PostGIS type of desired measure |
| numer_colname | Internal identifier for column name |
| numer_tablename | Internal identifier for table |
| numer_geomref_colname | Internal identifier for geomref column name |
| denom_id | Identifier for desired normalization. |
| denom_timespan | Timespan that will be used of the desired normalization. |
| denom_name | Human-readable name of desired measure's normalization |
| denom_type | PostgreSQL/PostGIS type of desired measure's normalization |
| denom_colname | Internal identifier for normalization column name |
| denom_tablename | Internal identifier for normalization table |
| denom_geomref_colname | Internal identifier for normalization geomref column name |
| geom_id | Identifier for desired boundary geometry. |
| geom_timespan | Timespan that will be used of the desired boundary geometry. |
| geom_name | Human-readable name of desired boundary geometry's |
| geom_type | PostgreSQL/PostGIS type of desired boundary geometry |
| geom_colname | Internal identifier for boundary geometry column name |
| geom_tablename | Internal identifier for boundary geometry table |
| geom_geomref_colname | Internal identifier for boundary geometry ref column name |
Examples
Obtain metadata that can augment with one additional column of US population data, using a boundary relevant for the geometry provided and latest timespan.
SELECT OBS_GetMeta(ST_Extent(the_geom),
'[{"numer_id": "us.census.acs.B01003001"}]')
Obtain metadata that can augment with one additional column of US population data, using census tract boundaries.
SELECT OBS_GetMeta(ST_Extent(the_geom),
'[{"numer_id": "us.census.acs.B01003001", "geom_id": "us.census.tiger.census_tract"}]')
Obtain metadata that can augment with two additional columns, one for total population and one for male population.
SELECT OBS_GetMeta(ST_Extent(the_geom),
'[{"numer_id": "us.census.acs.B01003001"}, {"numer_id": "us.census.acs.B01001002"}]')
OBS_GetData(geomvals array[geomval], metadata json)
The OBS_GetData(geomvals, metadata) function returns a measure and/or
geometry corresponding to the metadata JSON array for each every Geometry of
the geomval element in the geomvals array. The metadata argument must be
obtained from OBS_GetMeta(extent, metadata).
Arguments
| Name | Description |
|---|---|
| geomvals | An array of geomval elements, which are obtained by casting together a Geometry and a Numeric. This should be obtained by using ARRAY_AGG((the_geom, cartodb_id)::geomval) from the CARTO table one wishes to obtain data for. |
| metadata | A JSON array composed of metadata output objects from OBS_GetMeta(extent, metadata). The schema of the elements of the metadata JSON array corresponds to that of the output of OBS_GetMeta(extent, metadata), and this argument must be obtained from that function in order for the call to be valid. |
Returns
A TABLE with the following schema, where each element of the input geomvals
array corresponds to one row:
| Column | Type | Description |
|---|---|---|
| id | Numeric | ID corresponding to the val component of an element of the input geomvals array |
| data | JSON | A JSON array with elements corresponding to the input metadata JSON array |
Each data object has the following keys:
| Key | Description |
|---|---|
| value | The value of the measurement or geometry for the geometry corresponding to this row and measurement corresponding to this position in the metadata JSON array |
To determine the appropriate cast for value, one can use the numer_type
or geom_type key corresponding to that value in the input metadata JSON
array.
Examples
Obtain population densities for every geometry in a table, keyed by cartodb_id:
WITH meta AS (
SELECT OBS_GetMeta(ST_Extent(the_geom),
'[{"numer_id": "us.census.acs.B01003001"}]') meta)
SELECT id AS cartodb_id, (data->1->>'value') AS pop_density
FROM OBS_GetData((SELECT ARRAY_AGG((the_geom, cartodb_id)::geomval) FROM tablename),
(SELECT meta FROM meta))
Update a table with population densities
WITH meta AS (
SELECT OBS_GetMeta(ST_Extent(the_geom),
'[{"numer_id": "us.census.acs.B01003001"}]') meta),
data AS (
SELECT id AS cartodb_id, (data->1->>'value') AS pop_density
FROM OBS_GetData((SELECT ARRAY_AGG((the_geom, cartodb_id)::geomval) FROM tablename),
(SELECT meta FROM meta)))
UPDATE tablename
SET pop_density = data.pop_density
FROM data
WHERE cartodb_id = data.id
OBS_GetData(ids array[text], metadata json)
The OBS_GetData(ids, metadata) function returns a measure and/or
geometry corresponding to the metadata JSON array for each every id of
the ids array. The metadata argument must be obtained from
OBS_GetMeta(extent, metadata). When obtaining metadata, one must include
the geom_id corresponding to the boundary the ids refer to.
Arguments
| Name | Description |
|---|---|
| ids | An array of TEXT elements. This should be obtained by using ARRAY_AGG(col_of_geom_refs) from the CARTO table one wishes to obtain data for. |
| metadata | A JSON array composed of metadata output objects from OBS_GetMeta(extent, metadata). The schema of the elements of the metadata JSON array corresponds to that of the output of OBS_GetMeta(extent, metadata), and this argument must be obtained from that function in order for the call to be valid. |
For this function to work, the metadata argument must include a geom_id
that corresponds to the IDS found in col_of_geom_refs.
Returns
A TABLE with the following schema, where each element of the input ids array
corresponds to one row:
| Column | Type | Description |
|---|---|---|
| id | Text | ID corresponding to an element of the input ids array |
| data | JSON | A JSON array with elements corresponding to the input metadata JSON array |
Each data object has the following keys:
| Key | Description |
|---|---|
| value | The value of the measurement or geometry for the geometry corresponding to this row and measurement corresponding to this position in the metadata JSON array |
To determine the appropriate cast for value, one can use the numer_type
or geom_type key corresponding to that value in the input metadata JSON
array.
Examples
Obtain population densities for every row of a table with FIPS code county IDs (USA).
WITH meta AS (
SELECT OBS_GetMeta(ST_Extent(the_geom),
'[{"numer_id": "us.census.acs.B01003001", "geom_id": "us.census.tiger.county"}]') meta)
SELECT id AS fips, (data->1->>'value') AS pop_density
FROM OBS_GetData((SELECT ARRAY_AGG((fips) FROM tablename),
(SELECT meta FROM meta))
Update a table with population densities for every FIPS code county ID (USA).
WITH meta AS (
SELECT OBS_GetMeta(ST_Extent(the_geom),
'[{"numer_id": "us.census.acs.B01003001", "geom_id": "us.census.tiger.county"}]') meta),
data as (
SELECT id AS fips, (data->1->>'value') AS pop_density
FROM OBS_GetData((SELECT ARRAY_AGG((fips) FROM tablename),
(SELECT meta FROM meta)))
UPDATE tablename
SET pop_density = data.pop_density
FROM data
WHERE fips = data.id