Control Chart MR
==================

A control chart is a valuable tool for monitoring process stability, as it indicates when your process is out of control and helps identify the presence of special-cause variation. When special-cause variation occurs, it means the process is not stable and corrective action is required to address the underlying issues.

An MR control chart, also known as the Moving Range chart, is a statistical process control tool used to monitor processes where data is collected one observation at a time rather than in subgroups. It uses a moving window to obersve the chronological changes of the ranges of these moving window and demonstrate the measurements with abnormal variation from its neighbours. 

To perform the study, choose Quality > Control Chart MR

.. image:: images/ctrl_chart_mr1.png
   :align: center

- **Input Column**

  - **Values**: The column containing the process measurements to control. The values should be numerical, continuous, and in chronological order.
  - **Moving Range**: The moving window size to cover consecutive data points to be included in the pseudo subgroups.

- **X axis setting**: 

  - **X Label**: The label for the x-axis. By default, the label is the name of the measurement data column.
  - **Axis Label Column**: By default, the x-axis ticks will be labeled with the numerical order of the data points. To specify custom labels (for example, production time), select the column containing the information. The label column should have the same number of data points as the measurement column.
  - **Max Axes Labels**: When there are a large number of data points, use this setting to customize how many x-axis tick labels should be displayed. 

- **Y Axis Settings**: Customize y-axis labels. The first setting is for the top chart. The second setting is for the bottom chart.
- **Y Ref Lines**: Additional reference lines to be displayed on the charts. The first setting is for the top chart. The second setting is for the bottom chart. Separate multiple values by commas.

- **Known Historical Parameters**:

  - **Process Mean**: The mean of the measurements from historical data. If left blank, the study will calculate the mean value from the given data. Use this input when the process data are limited and expected to follow previous observations.
  - **Process SD**: The standard deviation of the measurements from historical data. If left blank, the study will calculate the value from the given data. Use this input when the process data are limited and expected to follow previous observations. The standard deviation and mean do not need to be input together.

- **All SD Lines**: By default, only limit lines of ±3 sigma will be displayed. Use this option to display 1 sigma and 2 sigma limits as well.


Please refer to the help page of `Control Chart I/MR <https://minijmp.readthedocs.io/en/latest/usage/ctrl_chart_imr.html>`_ about chart interpretation.