We have seen the following canvas before in the The Tableau Prep Builder GUI section. In this article we will take up Cleaning Data. We will divide the prepping features into five subcategories: cleaning, unions and joins, aggregating, pivoting, and scripting. I hope that by the end of this chapter you will be able to cut your time spent data prepping in half (at least). Sometimes I even use it for datasets I don’t want to visualize in Tableau Desktop, just to get a quick overview of, for example, how many rows contain a specific word, how many columns are needed, what happens to the date range if I filter a particular value, and so on! Within a few minutes I have insights that would have taken me much more time to get with database queries or Excel functions. To me, the best part about Tableau Prep Builder is that it can handle a huge amount of data. Fewer queries in Tableau Desktop means faster generation of dashboards. The fact is, the closer your Prep output data is to what you need for your Tableau Desktop visualization, the more efficiently VizQL will run on Tableau Desktop. It really depends on the dataset itself and the expected output. Other times you might just run an aggregation (one feature) and be done. Sometimes you might use many different tools to prepare your dataset in order to get it in the shape you desire. Tableau Prep Builder comes with lots of distinctive features. Next, we will continue by adding more data sources. The lower pane will always show the data source of the selection made at the row level. So far, we have seen that, after loading data in Prep, visual filters can be applied by clicking on a field or bar in one of the columns. Once you have selected the input data needed, click on the + in the flow pane and select Add: Clean Step. The data type options are, for example, strings, dates, or numbers. In the input pane samples (the section marked with D) you can select and deselect the fields you want to import and change their data types. Also, you can limit the sample set that Tableau Prep Builder will print to increase performance. In the input pane (the section marked with C) you can use the wildcard union (multiple files) function to add multiple files from the same directory. D: The input pane samples, showing the fields you moved to the connection pane, including sample values.C: The input pane settings, which give you several options to configure your input.B: The flow pane, which shows your current Prep flow.A: The connection pane, showing you the input files available at the location selected.
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