Explain the Table Calculation Function ' LOOKUP() ' in Tableau with Example?

In Tableau, the LOOKUP() function is a table calculation function that allows you to retrieve the value of a dimension or measure from a specified row or a specified number of rows away from the current row within a specified context or partition. The LOOKUP() function is useful for accessing values from different rows and can be used for various calculations and comparisons.

The syntax for the LOOKUP() function in Tableau is as follows:

LOOKUP(expression, [offset])

• expression: The field or calculation for which you want to retrieve the value.
• offset (optional): Specifies the number of rows away from the current row. Positive values indicate looking forward, while negative values indicate looking backward. If not specified, the default offset is 0, which refers to the current row.

Here's an example to demonstrate how to use the LOOKUP() function in Tableau:

Suppose you have a dataset that contains information about monthly sales for different products. You want to calculate the percentage change in sales compared to the previous month for each product.

1. Open Tableau and connect to your dataset.
2. Drag the "Product" field to the Rows shelf to create a table view with products.
3. Drag the "Month" field to the Columns shelf to display months horizontally.
4. Drag the "Sales" field to the Marks card to apply the aggregation. By default, Tableau will aggregate the sales using the SUM function.
5. Right-click on the "Sales" field in the Marks card and select "Add Table Calculation."
6. In the calculation dialog box, choose "LOOKUP" from the list of table calculation functions.
7. Specify the expression as the field or calculation for which you want to retrieve the value (in this case, "Sales").
8. Configure the specific settings for the LOOKUP function, such as the addressing and partitioning options.
9. Click "OK" to apply the LOOKUP function to the sales values.

Tableau will calculate the percentage change in sales compared to the previous month for each product based on the applied table calculation. You can further customize the view, apply sorting, or add additional calculations based on the LOOKUP values.

The LOOKUP function allows you to access values from different rows and perform calculations based on those values. It is commonly used for computing percentage changes, identifying trends, or comparing values between adjacent rows.

By utilizing the LOOKUP function in Tableau, you can perform dynamic calculations and comparisons that rely on values from different rows within your dataset.