# 1.1 Basic Mapping

Common map classifications include the **Quantile Map**, **Natural Breaks Map**, and **Equal Intervals Map**. Specialized classifications that are designed to bring out extreme values include the **Percentile Map**, **Box Map** (with two options for the hinge), and the **Standard Deviation Map**. The methods of map classification calculate a corresponding breakpoint list for a selected variable. For more information about the map classification, please read [http://geodacenter.github.io/workbook/6a\_local\_auto/lab6a.html](http://geodacenter.github.io/workbook/6a_local_auto/lab6a.html).

## 1. Natural Breaks

Natural Breaks calculates a list of breakpoints based on the fracture principle of maximum similarity within a group.&#x20;

### natural\_breaks()

**Synopsis**

```sql
float[] natural_breaks(numeric, integer)
```

**Example**

```sql
SELECT natural_breaks(hr60, 5) FROM natregimes;

                    natural_breaks                     
-------------------------------------------------------
 {3.3308906802,7.4689850396,13.450747147,31.426775613}
(1 row)
```

## 2. Quantile Breaks

Quantile Breaks is based on sorted values for a variable that are then grouped into bins that each have the same number of observations, the so-called quantiles.

### quantile\_breaks()

**Synopsis**

```sql
float[] quantile_breaks(numeric, integer)
```

**Example**

```sql
SELECT quantile_breaks(hr60, 5) FROM natregimes;

               quantile_breaks               
---------------------------------------------
 {0,1.7654960252,4.06106847805,7.9740054575}
(1 row)
```

## **3.** Percentile Breaks

Percentile Breaks divides the data into six ranges: the lowest 1%, 1-10%, 10-50%, 50-90%, 90-99% and the top 1%..

### quantile\_breaks()

**Synopsis**

```sql
float[] percentile_breaks(numeric)
```

**Example**

```sql
SELECT percentile_breaks(hr60) FROM natregimes;

               percentile_breaks               
-----------------------------------------------
 {0,0,2.7833299411,11.274974068,24.8236821873}
(1 row)
```

## 4. Hinge Box Breaks

Hinge Box Breaks calculates a list of breakpoints, including the top, bottom, median, and two quartiles of the data. The hinge values can be 1.5 or 3.0.&#x20;

### hinge15\_breaks()

**Synopsis**

```sql
float[] hinge15_breaks(numeric)
```

**Example**

```sql
SELECT hinge15_breaks(hr60) FROM natregimes;

                        hinge15_breaks                        
--------------------------------------------------------------
 {-10.32795220545,0,2.7833299411,6.8853014703,17.21325367575}
(1 row)
```

### hinge30\_breaks()

**Synopsis**

```sql
float[] hinge30_breaks(anyelement)
```

**Example**

```sql
SELECT hinge30_breaks(hr60) FROM natregimes;

                       hinge30_breaks                       
------------------------------------------------------------
 {-20.6559044109,0,2.7833299411,6.8853014703,27.5412058812}
(1 row)
```

## 5. Standard Deviation Breaks

Standard Deviation Breaks calculates the number of standard deviational units of the range from lowest to highest, returning a breakpoint list.

### stddev\_breaks()

**Synopsis**

```sql
float[] stddev_breaks(anyelement)
```

**Example**

```sql
SELECT stddev_breaks(hr60) FROM natregimes;

                                      stddev_breaks                                      
-----------------------------------------------------------------------------------------
 {-6.79536838828887,-1.14564656029265,4.50407526770356,10.1537970956998,15.803518923696}
(1 row)
```

##
