---
title: "Creating a Rating Table"
canonical: "https://docs.rubiconwater.com/space/DC/2048721188/Creating%20a%20Rating%20Table"
format: markdown
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> Macro (toc)

This procedure assumes that you have a source tag, for example, a tag holding water level data, from which you want to derive a value for another tag.

# Create a Tag for the Derived Value

- In the site for the source tag, create a tag in the site's SYSTEM table to hold the value derived from the rating table.
  See <u>[Creating a new tag](https://rubiconwater.atlassian.net/wiki/spaces/DCNC/pages/2048721008)</u> for more information.

# Create a Rating Table

**Step 1**

In the Rating Tables module click **Add** to create a new rating table.

**Step 2**

Enter the following details:

| **Property** | **Description** |
| --- | --- |
| Source Variable Tag | Specify the tag from which you want to read data (the X value). |
| Derived Variable Tag | Specify the tag whose value you want to determine from the equation or table (the Y value). |
| Equation | If you have been provided with an equation, select the **Equation** checkbox and enter the equation parameters. |
| Minimum/Maximum Values | Specify the minimum and maximum values for an equation based rating table. |
| Start/End Date | The start and end dates specify when the rating table is valid. By default, a rating table becomes valid when it is created and remains valid until it is updated, but you can set a specific validity period if you wish. |
| Interpolation Method | Specify the interpolation method to use when calculating values that fall between points on a data points table. Interpolation can be linear or logarithmic. |

**Step 3**

Click **Save** to save your changes.

# Add a Table of Points

If you are not using an equation, add points to the data points table.

- In the Points tab, either enter data points manually with the **Insert** function, or [import a file](https://rubiconwater.atlassian.net/wiki/spaces/DCNC/pages/2048753939) of data points.

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