Filters are applied to restrict the number of records present in the dataset. Filters can help to minimize the size of data sets for efficient use, eliminate irrelevant dimension elements, clean up underlying data, set date ranges and measures as required, simplify and organize data, etc. Without filters, sometimes data can’t be viewed as needed and hence results may not be accurate.
Filters are an important part of Tableau and there are different types of filters. They help in working with data and creating dashboards. Filters in general can be applied to specific worksheets and data structures, restricting the number of data points the visualization will present. Each filter in Tableau is used for different purposes. Filters are executed in the below order in Tableau.
Extract Filters: As the name implies extract filters are used to filter the data while creating the extract. Extract files are a local copy of a subset of the entire data source that you can be used to share data, work offline, and improve database performance. When we select the Extract option as a connection in the top right corner of the Tableau Desktop window, a dialogue box appears that shows the data to be extracted and filters can be applied to it. Any other data which are not extracted at this stage is not available for reporting. There are a few other options like aggregate data for visible dimensions, roll up to dates, hide unused files, etc. which can be applied while using extract filters. Ex. To extract the data only for a specific region, extract filters can be applied. And all the other regions cannot be seen as we have extracted the data for a specific region.
Data Source Filters: A data source filter is used to filter the data at the data source level. It can restrict the records present in the data set. This filter is similar to the extract filter for securing the data. But data source filters and extract filters are not linked to each other. They are completely independent of one another. For users that go back to a live connection, the data source filter will remain active. The data source filter works on both live and extract connections.
Context Filters: Context filters execute before any other filters in the worksheet other than extract and data source filters. The context filter is an independent filter and all the other filters will be applied to the data that is fetched by the Context filter. Datasets are reduced efficiently to provide the viewer with all data rows despite the constraints. The context filter in Tableau adds an actionable connection to the data report. If the data is not reduced, the cost of computing will be increased and sometimes inaccurate too.
Dimension Filters: When a dimension is used to filter the data in a worksheet, it is called a Dimension filter. It is a non-aggregated filter where a dimension, group, sets, and the bin can be added. A dimension filter can be applied through the top or bottom conditions, wildcard match, and formula. If there are too many dimensions, an individual can search for them through the panel. The filter provides four possibilities, General, Wildcard, viz, and Condition. Users can select one or more and eliminate the undesired data. You can create your formulas, unique to your workload, and then use them in the Condition filter and the Top/Bottom filter for data selection. They provide an extra channel to get the required data.
Measure Filters: A measure filter can filter the data based on the values present in a measure. The aggregated measure values can be used in the measure filter to modify the data. Using a Measure filter in Tableau allows users to perform various actions and extra functions. Some of the mathematical functions are sum, median, average, standard deviation, etc. The filters are implemented to measure fields that collect quantitative data.
Once applied, the next stage of the process will liberate a dialog box, that will give the user four extra types of filters:
Range: Select the range of values.
At least: Select the minimum value of a measure.
At most: Select the maximum value of a measure.
Special: Select null or non-null values.
6. Table Calculation Filters: The table Calculation filter is the last filter that is applied after the view has been created. Table calculations are a special type of calculated field that computes the local data in Tableau. They are calculated based on what is currently in the visualization and do not consider any measures or dimensions that are filtered out of the visualization.