The layer comparison functionality allows you to quickly compare tags of interest for different periods of concern, in a numerical and visual way. You will need to create and overlay different layers or periods in order to perform a numerical layer comparison.
In practice the layer comparison functionality can be used to:
- Determine root causes by overlaying good and bad periods, numerically compare layers and browse for differences:
- Searching for a bad situation → Look for the root cause
- Searching for all the periods (batches, campaigns) → Reorder them into good and bad ones
- Gain process insights by comparing different regimes of operation
- Quickly identify periods with the highest throughput, efficiency
This article describes how to use the layer comparison table and the different statistical parameters available for layer comparison.
- How to use the comparison table
- Statistical parameters
- Layer table options
How to use the layer comparison table
- Load in all relevant tags you want to analyze.
- Navigate to the time period you want to analyze.
- Overlay other time periods you want to compare.
- Click on the "Compare layers" button situated within the new view bar above the focus chart.
Different parameters for performing a layer comparison are available. The 'Average values' option is selected by default. The different measurements are categorised into key parameters and similarity parameters.
By clicking on the cog situated at the top right of your table, a side panel appears from the right displaying the "Edit table" options.
Select either a key parameter or similarity parameter. Your selection is denoted in the second column of the compare layer table.
Note: You can also select the number of decimal places the data displays and whether or not to display units.
The layer compare table compares the key values of the corresponding tag (row) within the corresponding layer (column). Additionally, the difference with respect to the reference layer (light grey column) is displayed.
- Average values
- Standard deviation
- Minimum values
- Maximum values
- Range values
- Integral values
- Start values
- Delta values
An overview of all similarity measures available are listed below:
- 'Statistical similarity': each table cell displays a measure of similarity between; A) the distribution of values of the corresponding tag (row) within the corresponding layer (column) and B) the distribution of values of the same tag (row) within the reference layer (light grey column). The similarity score is based on an adapted Kolmogorov–Smirnov test statistic.
- 'Evolution similarity': each table cell displays a measure of similarity between; A) the evolution of the corresponding tag (row) within the corresponding layer (column) and B) the evolution of the same tag (row) within the reference layer (light grey column).
- 'Correlation': each table cell displays the Pearson correlation coefficient between; A) the evolution of the corresponding tag (row) within the corresponding layer (column) and B) the evolution of the same tag (row) within the reference layer (light grey column).
Note: Statistical data for each layer is a comparison to the layer selected as the base.
Note: The base layer (or reference layer) is denoted with a blue boxed B in the title cell of the layer column.
For key parameters, the difference of each layer parameter with respect to the reference layer (light grey column) is displayed in each cell. Positive differences are shown in light orange and negative differences in light blue.
For the similarity measures, data is only displayed for non-reference layers. In the following table, the base layer is layer three and the similarity measure selected is "Statistical". Columns for Layers one and two are displaying statistical similarity to Layer three.
Note: While live mode is enabled, the compare layers table is no longer updated automatically. In this instance a small refresh button appears in the header of the tags column of the compare layer table. Use this to update your table.
Layer table options
By clicking on the three vertical dots situated to the right of a layer name you open a drop down menu that provides a few layer options.
- Hide layer
- Rename layer
- Set as base layer
Note: Actions taken here update the layers menu situated left of the focus chart.
Note: A change in base layer triggers a recalculation of the statistics in the compare layer table.
Each column of the layer comparison table holds a sorting option. When you click on the column heading a small arrow appears. By clicking on the arrow you can choose to sort your columns ascending or descending. The tag sorting option of the table is one rule above the tag menu. This means that you can sort your tags list in your layer table, and it will not affect the tag list in the tag menu or focus chart. However, if you sort or rearrange the tags in your tag menu the arrangement of your tags in the focus chart will mirror the changes seen in your tag menu, if no sorting is applied on any table columns.