Welcome

LOD Is the Key (to asking the right questions)

Ross Bunker

Principal Engineer

Tableau Software

# L O D I S T H E K E Y

Agenda

Why does LOD Matter?

What is LOD?

LOD in Tableau: A History

LOD in Tableau: The Future

Why does LOD matter?

If you do not know how to ask the right question, you discover nothing.

—W. Edwards Deming

If Tableau doesn’t let you ask the right question, you discover nothing.

—Me

What is the Question?

What are the total sales of each product? (Help me see by product type too)

What is the Question?

What is the salary of employees in each call center region?

The Replication Problem…

What is the salary of employees in each call center region?

What is LOD?

Totally Aggregated

Totally Disaggregated

(granularity of data source -

cannot go lower)

Dimensions determine the granularity of your

measurements. They are the characteristics

of the objects you are measuring

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Dimensions

Measures

Credit: Alan Eldridge, Sales Consultant Extraordinaire

What is LOD?

Many ‘things’ in a purchase order:Salesperson

Producer

Purchaser

Products

Company

State (salesperson)

State (purchaser)

State (producer)

Time (order date)

Time (ship date) not pictured

What is LOD?

Simple questions I might ask:

Total sales by date?

Unit of product X sold?

Highest volume

producer in each state?

Zip codes with

most purchases?

For this Given Set of Characteristics of These Things, What is My Measurement?

LOD is the Set of ‘Characteristics’ You Use to Define the ‘Things’ You are Measuring

LOD in Tableau:A History

Totally Aggregated

Totally Disaggregated

(granularity of data source -

cannot go lower)

Tableau’s data model exposes a single flat

table as the LOD of the data source.

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Credit: Alan Eldridge, Sales Consultant Extraordinaire

Row LOD

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Credit: Alan Eldridge, Sales Consultant Extraordinaire

Viz Level of Detail

Dimensions in Viz

Viz LOD brings data from the ‘source’ LOD

to the LOD of my question. Viz is the

question and defines the LOD

Viz LOD

What are the total sales of each product? (Help me see by product type too)

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Totally Aggregated

Totally Disaggregated

(granularity of data source -

cannot go lower)

Features that let you summarize:

totals, ref lines, table calcs, etc.

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Credit: Alan Eldridge, Sales Consultant Extraordinaire

Viz Level of Detail

Dimensions

Summary LOD

Summary LOD

How do my individual product sales compare to the average sales for all products?

> 1000

SUM(Sales)

Customers

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Totally Aggregated

Totally Disaggregated

(granularity of data source -

cannot go lower)

Filters let you compute small

things at specific LOD.

(SUM(Sales) > 1000, Top N)

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Credit: Alan Eldridge, Sales Consultant Extraordinaire

Viz Level of Detail

Dimensions

Filter LOD

How do sales of products fluctuate over time for products with lifetime sales > 40k?

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Totally Aggregated

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Credit: Alan Eldridge, Sales Consultant Extraordinaire

Viz Level of Detail

Dimensions in Viz

Extract at LOD let’s you redefine the

‘source’ LOD to reduce the amount of data

in your extract and improve performance

Extract Level of Detail

Extract LOD

What are my average monthly sales for each year/quarter?

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Credit: Alan Eldridge, Sales Consultant Extraordinaire

Viz Level of Detail

Dimensions in Viz

Geocoding lets you combine data based

on a subset of the LOD. LOD must be in

the viz. Data is replicated to VizLOD

State Latitude Longitude

WA 47.50 -120.50

OR 44.00 -120.5-

Geocoding

What is the sum of sales in each state and how does it vary by product type?

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Credit: Alan Eldridge, Sales Consultant Extraordinaire

Viz Level of Detail

Join LOD

Data Blending is a generalization of

geocoding. Arbitrary data aggregated to

a compatible LOD, joined, and replicated

(if necessary) to Viz LOD

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Blending

How are my regional sales doing vs. quota?

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Credit: Alan Eldridge, Sales Consultant Extraordinaire

Viz Level of Detail

Join LOD

Data Blending was then extended to

support blending on dimensions not in

the viz. This introduced a ‘BlendLOD’

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Blending at Join LOD

What is my profitability in each sales territory?

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Totally Aggregated

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cannot go lower)

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Credit: Alan Eldridge, Sales Consultant Extraordinaire

Viz Level of Detail

Dimensions in Viz

Fixed LOD Expressions are

computed at a particular LOD,

then joined into the other results

at a compatible LOD

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When used as a dimension, the

values are replicated at the data

source granularity

When used as a measure, the values

are joined at the LOD that causes the

least amount of replication and results

are then aggregated to VizLOD

LOD Calculations

Does the month in which a customer makes an initial purchase affect long term spend?

Asking Questions Requires Multiple Levels of Detail

There is no single view.

—Jock Mackinlay and Chris Stolte

There is no single LOD.

—Me

Questions that are Cumbersome from PO Data

What is my employee sales/salary ratio?Salary information is replicated to order LOD, need LOD calc to un-replicate

What employees have no sales in some months?Data is sales, so doesn’t show rows with employee and month if employee had no sale

Where are my customers relative to my stores?Plotting both on the same map today requires a join, but I want to show each independently

What is the average sales of my top ten customers in each state, compared to the rest of the customers in the state?

Ranking isn’t available in the database

LOD in Tableau:The Future

Future Improvements in Tableau

Richer computations even when not supported by the underlying database

Ability to combine data sources with different LODs into the same visualization without requiring a blend

Richer data modelling to support data sources that contain information at multiple levels of detail

Thank you!

#TC18

Ross Bunker

Principal Engineer

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