Input Step

After connecting to a data source, select the input by dragging the data source from the Connections pane onto the canvas. By default, Prep Builder samples the input data set to speed up the process of building your workflow. When you run the workflow when an output is set up, all of the data will automatically be processed. The Input step is shown in Figure 2-6.

Figure 2-6. Prep Builder’s Input step screen

The three key parts of this screen (excluding the Connections pane) are:

Flow pane (top)

This area reflects the current step of the data preparation process.

Input pane (gray area)

This is where you set up the input. You can use multiple files and choose how the data is sampled as you are building the flow. Prep keeps a log of changes you make during this step.

Data fields (white table)

This is where you select the specific data categories to bring into the data preparation flow. You can change the names of the data fields (columns) or alter the data types. Prep displays a small subset of sample values to help you understand what each column contains.

Clean Step

The Clean step is where the majority of the work takes place, so getting familiar with it is key to your overall understanding of Prep Builder. To begin the Clean step, click the plus sign to the right of the selected input data, as shown in Figure 2-7.

Figure 2-7. Prep Builder’s Clean step screen

There are four key parts to this screen, including the Connections and Flow panes. The other two are:

Profile pane (center)

Prep takes the sample of the data you set up during the Input step and distributes it in the appropriate data field of your data set. You can complete a number of preparation tasks within the Profile pane by selecting certain values. For example, to examine the relationships between values, select one value in a data field and see what values also appear in that row.

Data grid (bottom)

Here you can see the records (rows) of your data set. There are three icons at the top right of the Profile pane where you can change how your data is displayed in the Data pane (Figure 2-8): the Profile pane and Data grid; just the Data grid; or the List view, which shows the metadata of the data set.

Figure 2-8. The data view options (left to right: the Profile pane and Data grid, Data grid only, and List view)

Output Step

Once you have cleaned the data, you can output the data set to make it available for analysis in other tools (Figure 2-9).

Figure 2-9. Adding an Output step

The Output step gives you a number of choices about how to output your data. Part IV of this book is dedicated to outputs, with a focus on outputting to files in Chapter 19 and to databases in Chapter 20. The default option for the output is to save to a file in your My Tableau Prep Repository folder.

Saving a Flow

Whether you have completed your flow or just need to pause your work to continue later, saving the flow is key. To do so, select Save or Save As from the menu at the top of the screen (Figure 2-10).

Figure 2-10. Saving a flow file

When saving the file, you’ll see a screen where you have two choices for the file type (Figure 2-11):

• Tableau flow file (.tfl) saves the logic of the flow as well as the input and output file locations. Therefore, you’ll need access to the input and output locations to make use of this file format.

• Packaged Tableau flow file (.tflx) saves not just the logic but also the input and output files.

Figure 2-11. Saving to a file in Prep

Once you’ve selected a save option, you can process the flow by clicking the run icon (▷) either at the top of the Flow pane (to run every output) or on the output step icon (to run a single output), as shown in Figure 2-12.

Figure 2-12. Processing a flow with the run icon