From 1be0aa8330f089bb1276a684fb95086c3d2218e4 Mon Sep 17 00:00:00 2001
From: Andy Eschbacher <andy.eschbacher@gmail.com>
Date: Wed, 4 Jan 2017 16:37:09 -0500
Subject: [PATCH] adding docs for gwr

---
 doc/21_gwr.md | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 doc/21_gwr.md

diff --git a/doc/21_gwr.md b/doc/21_gwr.md
new file mode 100644
index 0000000..99f41ff
--- /dev/null
+++ b/doc/21_gwr.md
@@ -0,0 +1,50 @@
+## Regression
+
+### Geographically weighted regression
+
+Can currently estimate Gaussian, Poisson, and logistic models (built on a GLM framework). GWR object prepares model input. Fit method performs estimation and returns a GWR Results object.
+
+#### Arguments
+
+| Name | Type | Description |
+|------|------|-------------|
+| subquery | text | SQL query that expose the data to be analyzed (e.g., `SELECT * FROM regression_inputs`). This query must have the geometry column name (see the optional `geom_col` for default), the id column name (see `id_col`), dependent and independent column names. |
+| dep_var | text | name of the dependent variable in the regression model |
+| ind_vars | text[] | Text array of independent used in the model to describe the dependent variable |
+| bw (optional) | numeric | bandwidth value consisting of either a distance or N nearest neighbors. Defaults to calculate an optimal bandwidth. |
+| fixed (optional) | boolean | True for distance based kernel function and False for adaptive (nearest neighbor) kernel function (default). Defaults to false. |
+| kernel | text | Type of kernel function used to weight observations. One of gaussian, bisquare (default), or exponential. |
+
+
+#### Returns
+
+| Column Name | Type | Description |
+|-------------|------|-------------|
+| coeffs | JSON | JSON object with parameter estimates for each of the dependent variables. The keys of the JSON object are the dependent variables, with values corresponding to the parameter estimate. |
+| stand_errs | JSON | Standard errors for each of the dependent variables. The keys of the JSON object are the dependent variables, with values corresponding to the respective standard errors. |
+| t_vals | JSON | T-values for each of the dependent variables. The keys of the JSON object are the dependent variable names, with values corresponding to the respective t-value. |
+| predicted | numeric | predicted value of y |
+| residuals | numeric | residuals of the response |
+| r_squared | numeric | R-squared for the parameter fit |
+| bandwidth | numeric | bandwidth value consisting of either a distance or N nearest neighbors |
+| rowid | int | row id of the original row |
+
+
+#### Example Usage
+
+```sql
+SELECT
+  g.cartodb_id,
+  g.the_geom,
+  g.the_geom_webmercator,
+  (gwr.coeffs->>'pctblack')::numeric as coeff_pctblack,
+  (gwr.coeffs->>'pctrural')::numeric as coeff_pctrural,
+  (gwr.coeffs->>'pcteld')::numeric as coeff_pcteld,
+  (gwr.coeffs->>'pctpov')::numeric as coeff_pctpov,
+  gwr.residuals
+FROM cdb_crankshaft.CDB_GWR('select * from g_utm'::text, 'pctbach'::text, Array['pctblack', 'pctrural', 'pcteld', 'pctpov']) As gwr
+JOIN g_utm as g
+on g.cartodb_id = gwr.rowid
+```
+
+Note: See [PostgreSQL syntax for parsing JSON objects](https://www.postgresql.org/docs/9.5/static/functions-json.html).