---
title: Use the XMR Chart Function
slug: litmusedge/how-to-guides/analytics-guides/xmr-chart-function
description: Learn how to use the XMR Chart function in Analytics. 
docTags: 
createdAt: 2024-02-29T21:32:29.941Z
---

You can use the XMR Chart function to calculate a central line that remains constant.  

The central line is utilized to monitor the consistency and fluctuation of a process over a period of time. It comprises two distinct charts: 

- **Individual (X) Chart:** Used to trace individual values.
- **Moving Range (MR) chart:** Used to observe the variation between consecutive measurements.

# User Scenario

Review the following scenario for the XMR Chart function. Then, you will simulate PLC data and calculate the central line.

In a pharmaceutical production plant, consistent dosage in pill manufacturing is paramount for patient safety and regulatory compliance. High-precision scales measure the weight of individual pills, with data points collected at regular intervals. 

The XMR Chart function is integral to this process, providing real-time monitoring of dosage weights. By establishing a central line from initial measurements and calculating moving ranges, the plant ensures each pill is within the stringent weight specifications. 

# Step 1: Add a Device

Follow the steps to [Connect a device](docId\:pal6ABPZbrimdU9LvGJ30) and configure the following parameters:

- **Device Type**: Simulator
- **Driver Name**: Generator
- **Enable Alias Topics**: Select the checkbox. 

# Step 2: Add Tags

After connecting the device, add the following tag. See [Add Tags](docId\:XgWOkQbTPevII7OR82LL0) to learn more. 

## Tag 1: input1

- **Name**: Select **S - Random value generator**
- **Value Type:** Select **float64**
- **Polling Interval**: Enter **1**
- **Tag Name**: Enter **input1**
- **Min\_value**: Enter **101**
- **Max\_value**: Enter **199**

# Step 3: Create Analytics Flows

You can now create the analytics flows using data from the device and tag you previously created. 

**To create an analytics flow with the XMR Chart Processor function:**

1. In Litmus Edge, navigate to **Analytics**. 
2. On the analytics canvas, click** Add processor**. 
   The *Create a processor* dialog box displays. 
   ::Image[]{src="https://api.archbee.com/api/optimize/SSUUxKZUk9bFTEPNn_6Zo/ZdcpDTjKPrLwdKeFw6LWq_base-conversionadd-processor.png" size="80" width="1244" height="452" caption="The Add processor option" position="center" showCaption="true"}
3. Select **DataHub Subscribe**.
4. In the **Topic **field, click the **Search **icon, select the device you previously created, and then select the alias topic for the **input1 **tag. 
   ![](https://api.archbee.com/api/optimize/SSUUxKZUk9bFTEPNn_6Zo/AdCgZcKlrYLXkOnUTBkWY_a.png "Create a Processor dialog box")
5. Click **Save**.
6. Click **Add processor** again and select the **XMR Chart **processor.
   The *Edit a Processor *dialog box appears.
   - **Window Size:** Enter a value that represents the range to apply the XMR chart function. For this example, we input a value of **100**.
   - **Process Limit Multiplier:** It is used to calculate the upper and lower process limits. For this example, we input a value of **2.66**.
   - **TimeInterval: **If you know your input is going to publish at the expected interval, it is better to disable this timer by entering **0** in the field.
   - Click **Save**.
     ![](https://api.archbee.com/api/optimize/SSUUxKZUk9bFTEPNn_6Zo/0t7cNz2vV0LU00N-I-N8O_image.png "Edit a Processor dialog box")
7. Connect the *DataHub Subscribe* processor (tag: *input1*) to the *XMR Chart* processor with a wire and use the **events **connection.
8. On the analytics canvas, click **Save**.
   The configured analytics flows should look like the following: 

![](https://api.archbee.com/api/optimize/SSUUxKZUk9bFTEPNn_6Zo/qA7pWRHmPxdYhH0ildw83_image.png "Completed Flows Canvas")

# Step 4: View Output of Processor

Click the **View **icon in the *XMR Chart *processor to view the output values.

The output of the XMR Chart function shows a central line at **150.29**, with an upper process limit of **229.14** and a lower process limit of **71.44**. ​

![](https://api.archbee.com/api/optimize/SSUUxKZUk9bFTEPNn_6Zo/vlBXHn-Uj8VYX2idzx077_image.png "Output of XMR Chart")

Once the window is filled, other fields that are calculated as follows: 

- **Moving Ranges:** Difference of successive values.
- **Average Moving Range: **Average of the moving ranges.
- **Process Limit Multiplier:** Calculates the upper and lower process limits.
- **Upper and Lower Natural Process limit: **Calculated by taking the product of process limit multiplier and average moving range, and adding/subtracting it from the central line.

In some cases, the central line is adjusted. Here are the cases:

- If current value is outside the process limits multiple times in a row.
- If the multiple values in a row are closer to either limit than they are to the central line.