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adds docs for obs_getmeasurebyid

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Andy Eschbacher 2016-05-24 13:28:21 -04:00
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doc/measures_functions.md
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@ -134,6 +134,40 @@ SET household_count = OBS_GetMeasure(the_geom, 'us.census.acs.B11001001')
* If an unrecognized normalization type is input, raise an error: `'Only valid inputs for "normalize" are "area" (default) and "denominator".` * 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](https://cartodb.github.io/bigmetadata/observatory.pdf))
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)
#### 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
```SQL
UPDATE tablename
SET household_count = OBS_GetMeasureById(geoid_column, 'us.census.acs.B11001001', 'us.census.tiger.county')
```
#### Errors
* Returns `NULL` if 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) ## 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](https://cartodb.github.io/bigmetadata/observatory.pdf) for more detail. 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](https://cartodb.github.io/bigmetadata/observatory.pdf) for more detail.