Profile data in Power BI
Profiling data is about studying the nuances of the data: determining anomalies, examining and developing the underlying data structures, and querying data statistics such as row counts, value distributions, minimum and maximum values, averages, and so on. This concept is important because it allows you to shape and organize the data so that interacting with the data and identifying the distribution of the data is uncomplicated, therefore helping to make your task of working with the data on the front end to develop report elements near effortless.
Assume that you are developing reports for the Sales team at your organization. You are uncertain how the data is structured and contained within the tables, so you want to profile the data behind the scenes before you begin developing the visuals. Power BI has inherent functionality that makes these tasks user-friendly and straightforward.
Examine data structures
Before you begin examining the data in Power Query Editor, you should first learn about the underlying data structures that data is organized in. You can view the current data model under the Model tab on Power BI Desktop.
On the Model tab, you can edit specific column and table properties by selecting a table or columns, and you can transform the data by using the Transform Data button, which takes you to Power Query Editor. Additionally, you can manage, create, edit, and delete relationships between different tables by using Manage Relationships, which is located on the ribbon.
Find data anomalies and data statistics
After you have created a connection to a data source and have selected Transform Data, you are brought to Power Query Editor, where you can determine if anomalies exist within your data. Data anomalies are outliers within your data. Determining what those anomalies are can help you identify what the normal distribution of your data looks like and whether specific data points exist that you need to investigate further. Power Query Editor determines data anomalies by using the Column Distribution feature.
Select View on the ribbon, and under Data Preview, you can choose from a few options. To understand data anomalies and statistics, select the Column Distribution, Column Quality, and Column Profile options. The following figure shows the statistics that appear.
Column quality and Column distribution are shown in the graphs above the columns of data. Column quality shows you the percentages of data that is valid, in error, and empty. In an ideal situation, you want 100 percent of the data to be valid.
[!NOTE By default, Power Query examines the first 1000 rows of your data set. To change this, select the profiling status in the status bar and select Column profiling based on entire data set. ]
Column distribution shows you the distribution of the data within the column and the counts of distinct and unique values, both of which can tell you details about the data counts. Distinct values are all values in a column, including duplicates and null values, while unique values do not include duplicates or nulls. Therefore, distinct in this table tells you the total count of how many values are present, while unique tells you how many of those values are not duplicates or nulls.
Column profile gives you a more in-depth look into the statistics within the column. This column provides several different values, including the count of rows, which is important when verifying whether the importing of your data was successful. For example, if your original database had 100 rows, you could use this row count to verify that 100 rows were, in fact, imported correctly. Additionally, this row count will show how many rows that Power BI has deemed as being outliers (and therefore "errors"), empty rows and strings, and the min and max, which will tell you the smallest and largest value in a column, respectively. This distinction is particularly important in the case of numeric data because it will immediately notify you if you have a maximum value that is beyond what your business identifies as a "maximum." This value calls to your attention these values, which means that you can then focus your efforts when delving deeper into the data. In the case where data was in the text column, as seen in the previous image, the minimum value is the first value and the maximum value is the last value when in alphabetical order.
Additionally, the Value distribution graph tells you the counts for each unique value in that specific column. When looking at the graph in the previous image, notice that the value distribution indicates that "Anthony Grosse" appears the greatest number of times within the SalesPerson column and that "Lily Code" appears the least amount of times. This information is particularly important because it identifies outliers. If a value appears far more than other values in a column, the Value distribution feature allows you to pinpoint a place to begin your investigation into why this is so.
On a numeric column, Column Statistics will also include how many zeroes and null values exist, along with the average value in the column, the standard deviation of the values in the column, and how many even and odd values are in the column. These statistics give you an idea of the distribution of data within the column, and are important because they summarize the data in the column and serve as a starting point to determine what the outliers are.
For example, while looking through invoice data, you notice that the Value distribution graph shows that a few salespeople in the SalesPerson column appear the same amount of times within the data. Additionally, you notice the same situation has occurred in the Profit column and in a few other tables as well. During your investigation, you discover that the data you were using was bad data and needed to be refreshed, so you immediately complete the refresh. Without viewing this graph, you might not have seen this error so quickly and, for this reason, value distribution is essential.
After you have completed your edits in Power Query Editor and are ready to begin building visuals, return to Home on the Power Query Editor ribbon. Select Close & Apply, which will return you to Power BI Desktop and any column edits/transformations will also be applied.
You have now determined the elements that make up profiling data in Power BI, which include loading data in Power BI, interrogating column properties to gain clarity about and make further edits to the type and format of data in columns, finding data anomalies, and viewing data statistics in Power Query Editor. With this knowledge, you can include in your toolkit the ability to study your data in an efficient and effective manner.