Add derivative integration

source/_components/derivative.markdown

@@ -0,0 +1,57 @@
+---
+title: "Derivative Sensor"
+description: "Instructions on how to integrate Derivative Sensor into Home Assistant."
+ha_category:
+  - Utility
+  - Energy
+ha_release: 0.105
+ha_iot_class: Local Push
+logo: derivative.png
+ha_qa_scale: internal
+---
+
+The `derivative` platform provides the numerical derivative or numerical differentiation of the values provided by a source sensor. Derivative sensors are updated upon changes of the **source**. Fast sampling source sensors provide better results. 
+
+## Configuration
+
+To enable Derivative Sensor in your installation, add the following to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: derivative
+    source: sensor.current_speed
+```
+
+{% configuration %}
+source:
+  description: The entity ID of the sensor providing numeric readings
+  required: true
+  type: string
+name:
+  description: Name to use in the frontend.
+  required: false
+  default: source entity ID meter
+  type: string
+round:
+  description: Round the calculated derivative value to at most N decimal places.
+  required: false
+  default: 3
+  type: integer
+unit_prefix:
+  description: Metric unit to prefix the derivative result. Available units are k, M, G, T.
+  required: false
+  default: None
+  type: string
+unit_time:
+  description: SI unit of time to integrate over. Available units are s, min, h, d.
+  required: false
+  default: h
+  type: string
+unit:
+  description: Unit of Measurement to be used for the derivative.
+  required: false
+  type: string
+{% endconfiguration %}
+
+If 'unit' is set then 'unit_prefix' and 'unit_time' are ignored.