Corr Studies

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Tableau 10.2 came out a couple weeks ago and a small but notable feature included in this version of our product is the Corr() and Window_Corr() functions. These calculations compute a coefficient of correlation based on two variables. I’ve done linear algebra in Tableau before, and it’s often quite complicated and looks like this:   The idea with making Corr a simple function in Tableau is to give users a faster and simpler way to find statistical results. But I was confused. correlation coefficients operate on large groups of numbers, so why would it make sense to aggregate a pair of measures with Corr()? How would the aggregation change based on the layout of a Tableau worksheet? And how could I check the results to make sure I was seeing the correlation coefficient I wanted to see? When doing complex calculations, you often get a seemingly arbitrary number as a result, and some faith is required to trust that the number is answering the question you intended to ask, and not a different question. Below are some findings from my Corr studies: A quick preamble about my math background. I was always pretty good at math growing up, but I […]

The Simplest Way and The Best Way: How Tableau Consultants Learn

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“You answered the question correctly, but you lost the sale.” I’m 26 years old and I’ve been working at Tableau for approximately 6 months. I’m on the phone with Marc Rueter who is dialing in from an undisclosed location (i.e. across the hall) in the Lakeview building, Fremont, Washington, the 4th floor of which houses the entirety of Tableau Software, Inc. presently in the summer of 2011. Those of us who worked at Tableau at this time, particularly the technical experts, consider Marc Rueter to be something of a god. He designed the Product Consultant role that was my entry-level job at the firm, and he defined the strategy behind all of Tableau’s training, pre-sales consulting, services delivery, and more as the company emerged as a startup. Marc interviewed me, hired me, mentored me, and now was proctoring my Gold Certification, the highest level of internal product certification Tableau offers. I had invested weeks into preparing for the technical questions he would ask, which started from a common list of prepared challenges but quickly spun into off-the-rails and improvised challenges designed to hurt your confidence and test your ability to adapt when dealing with a particularly difficult customer. Sometimes the […]

The Second Principle of Calcs: Logic

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In my last article we talked about aggregation. This is the most important principle of calculations in Tableau. As you’ll see, aggregation affects every other concept in calculations. Want to understand Table Calculations or LODs? You’d better damn well understand how Tableau aggregates data. But those are topics for a future post. You aren’t ready. Today we’re going to discuss logic and how it impacts calculations in Tableau. What Does Logic Mean When You’re Writing Calculations? “Logic” is a very abstract, nebulous term. I am being intentionally vague right now. We are not going to cover the difficult, theoretical concept of logic that you may have taken a course on during the process of obtaining your liberal arts degree. Though as a holder of a liberal arts degree myself the concept is intriguing. We are going to talk about using logic as part of your calculations in Tableau. And I know you will be surprised to hear this but logic in Tableau has a great deal to do with aggregation. Crack open the Tableau calculated field dialog box and filter the syntax to “Logical” and you’ll see this: This window is full of logical operators like “If” “And” and “Then” […]

Tableau Calculations: The Most Important Principle

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On our recent podcast Wilson and I alluded to a curriculum for someone looking to understand Tableau’s calculations more fully. We agreed that the first step was an understanding of how data can be aggregated. Here is lesson one. Aggregation and Tables People who have worked with databases extensively have an innate knowledge of this but the great thing about Tableau is that you don’t have to have DBA experience in order to understand it. So sometimes it’s important to go back to basics and really make sure really know what you’re doing when you aggregate data. Tableau works with tables of data like this*: *Actually, Tableau deals with lots of types of data sources. Excel tables look like this, but databases are often made up of lots of tables you have to combine. And some data sources like Hadoop don’t store data in tables at all. But regardless, Tableau uses some process to turn data into a table behind the scenes. When you drag and drop a measure in Tableau (in this case, Sales Amount is our measure), it is automatically aggregated. The default is as a sum. Other aggregations are Averages, Minimums, Maximums, Standard Deviations, etc. These are […]