Category: Big Data & Analytics

Tableau – Bump Chart ”; Previous Next A Bump Chart is used to compare two dimensions against each other using one of the Measure value. They are very useful for exploring the changes in Rank of a value over a time dimension or place dimension or some other dimension relevant to the analysis. The Bump Chart takes two dimensions with zero or more measures. Creating a Bump Chart Using the Sample-superstore, plan to find the variation of ship mode of products with the variation of the Sub-Category. To achieve this objective, following are the steps. Step 1 − Drag and drop the dimension Sub-Category to the Columns shelf. Also drag the dimension Ship mode to the Color shelf under Marks card. Leave the chart type to Automatic. The following chart appears. Step 2 − Next, create a calculated field called Rank. Go to Analysis → Create Calculated Field. Use Rank as the field name and write the expression index () in the calculation area. It is an inbuilt function that creates an index for the current row in the partition. Click OK and the new field will be visible in the measures section. Right-click on the field Rank and convert it to discrete. Step 3 − Drag Rank to the Rows shelf. The following chart appears which shows the dimension Sub-Category with each ship mode arranged in an increasing order of their Rank value. Step 4 − Apply some more calculation to the rank field using the measure Profit. Rightclick on Rank and choose Edit Table calculation. Choose the sorting by the field profit using partition by Sub-Category and addressed by ship mode. The following screenshot shows the calculations applied. On completion of the above steps, you will get the bump chart as shown in the following screenshot. It shows the variation of profit for each ship mode across various subcategories. Print Page Previous Next Advertisements ”;

Tableau – Functions ”; Previous Next Any data analysis involves a lot of calculations. In Tableau, the calculation editor is used to apply calculations to the fields being analyzed. Tableau has a number of inbuilt functions which help in creating expressions for complex calculations. Following are the description of different categories of functions. Number Functions String Functions Date Functions Logical Functions Aggregate Functions Number Functions These are the functions used for numeric calculations. They only take numbers as inputs. Following are some examples of important number functions. Function Description Example CEILING (number) Rounds a number to the nearest integer of equal or greater value. CEILING(2.145) = 3 POWER (number, power) Raises the number to the specified power. POWER(5,3) = 125 ROUND (number, [decimals]) Rounds the numbers to a specified number of digits. ROUND(3.14152,2) = 3.14 String Functions String Functions are used for string manipulation. Following are some important string functions with examples Function Description Example LEN (string) Returns the length of the string. LEN(“Tableau”) = 7 LTRIM (string) Returns the string with any leading spaces removed. LTRIM(” Tableau “) = “Tableau” REPLACE (string, substring, replacement) Searches the string for substring and replaces it with a replacement. If the substring is not found, the string is not changed. REPLACE(“GreenBlueGreen”, “Blue”, “Red”) = “GreenRedGreen” UPPER (string) Returns string, with all characters uppercase. UPPER(“Tableau”) = “TABLEAU” Date Functions Tableau has a variety of date functions to carry out calculations involving dates. All the date functions use the date_part which is a string indicating the part of the date such as – month, day, or year. Following table lists some examples of important date functions. Function Description Example DATEADD (date_part, increment, date) Returns an increment added to the date. The type of increment is specified in date_part. DATEADD (”month”, 3, #2004-04-15#) = 2004-0715 12:00:00 AM DATENAME (date_part, date, [start_of_week]) Returns date_part of date as a string. The start_of_week parameter is optional. DATENAME(”month”, #200404-15#) = “April” DAY (date) Returns the day of the given date as an integer. DAY(#2004-04-12#) = 12 NOW( ) Returns the current date and time. NOW( ) = 2004-04-15 1:08:21 PM Logical Functions These functions evaluate some single value or the result of an expression and produce a boolean output. Function Description Example IFNULL (expression1, expression2) The IFNULL function returns the first expression if the result is not null, and returns the second expression if it is null. IFNULL([Sales], 0) = [Sales] ISDATE (string) The ISDATE function returns TRUE if the string argument can be converted to a date, and FALSE if it cannot. ISDATE(“11/05/98”) = TRUE ISDATE(“14/05/98”) = FALSE MIN(expression) The MIN function returns the minimum of an expression across all records or the minimum of two expressions for each record. Aggregate Functions Function Description Example AVG(expression) Returns the average of all the values in the expression. AVG can be used with numeric fields only. Null values are ignored. COUNT (expression) Returns the number of items in a group. Null values are not counted. MEDIAN (expression) Returns the median of an expression across all records. Median can only be used with numeric fields. Null values are ignored. STDEV (expression) Returns the statistical standard deviation of all values in the given expression based on a sample of the population. Print Page Previous Next Advertisements ”;

Tableau – Numeric Calculations ”; Previous Next Numeric calculations in Tableau are done using a wide range of inbuilt functions available in the formula editor. In this chapter, we will see how to apply calculations to the fields. The calculations can be as simple as subtracting the values of two fields or applying an aggregate function to a single field. Following are the steps to create a calculation field and use numeric functions in it. Create Calculated Field While connected to Sample-superstore, go to the Analysis menu and click ‘Create Calculated Field’, as shown in the following screenshot. Calculation Editor The above step opens a calculation editor which lists all the functions that is available in Tableau. You can change the dropdown value and see only the functions related to numbers. Create a Formula To study the difference between profit and discount for different shipping mode of the products, create a formula subtracting the discount from the profit as shown in the following screenshot. Also, name this field as profit_n_discount. Using the Calculated Field The above calculated field can be used in the view by dragging it to the Rows shelf as shown in the following screenshot. It produces a bar chart showing the difference between profit and discount for different shipping modes. Applying Aggregate Calculations In a similar manner as above, you can create a calculated field using aggregate function. Here, create AVG(sales) values for different ship mode. Write the formula in the calculation editor as shown in the following screenshot. On clicking OK and dragging the Avg_Sales field to the Rows shelf, you will get the following view. Print Page Previous Next Advertisements ”;

Tableau – Add Worksheets ”; Previous Next Worksheet in the Tableau screen is the area where you create the views for data analysis. By default, Tableau provides three blank worksheets when you have established a connection to data source. You can go on adding multiple worksheets to look at different data views in the same screen, one after another. Adding a Worksheet You can add a worksheet in two ways. Right-click on the name of the current worksheet and choose the option New Worksheet from the pop-up menu. You can also click on the small icon to the right of the last sheet name to add a worksheet. Quick Preview of a Worksheet Staying in one worksheet, you can have a quick preview of another worksheet by hovering the mouse on the name of the other worksheet. Print Page Previous Next Advertisements ”;