Basics of Reading Data

1. Understanding Basic Data Concepts
- 1-1. Data Sources
- 1-2. Data Field
2. Understanding Data Structure Details
- 2-1. Granularity and Aggregation in Tableau
- 2-2. How data is represented in Tableau
  - 1. Dimensions & Measures
  - 2. Discrete & Continuous
3. Reading Common Chart Types
- 3-1. Overview to reading charts

1. Understanding Basic Data Concepts

>> Common types of data sets

Spreadsheets:
- e.g.: Excel, Google Sheets
- the records are stored as single rows of data
Relational Databases:
- store data in multiple tables
- “relational”: logical connection between tables
- users pull data from different tables using SQL
Cloud Data:
- e.g.: AWS, Microsoft Azure, Salesforce
Other Types:
- .kml, .shp, created in R

>> A field = A column

>> Data Field automatically assigned a Role and a Type

Role: “Dimension” or “Measure”
- Dimension: qualitative fields / (categorical data) * blue in tableau
- Measure: quantitative fields / (numerical data) * green in tableau
Type: String, Integer, Date, Date&Time, Boolean, Geographic, Mixed or cluster

>> Data granularity(数据粒度): the level of detail for a piece of data

>> move dimensions & measures in /out of a view --> level of details changes

>> “SUM(Profit)/SUM(Sales)” VS "Profit/Sales"

Caution the trap of granularity when aggregating

“SUM(Profit) / SUM(Sales)” [correct]
1. first sums the profits and sales to whatever the granularity of the view is
2. then computes the ratio at that aggregation
“Profit / Sales” [incorrect]
1. first compute the profit ratio at the lowest level of granularity
2. then sum the ratio to the requested aggregation of the view

Measures: aggregations

- aggregated up to the granularity set by the dimensions in the view
Dimensions: categorical fields

- set the granularity, or the level of detail

	Discrete	Continuous
Value	have distinct, separate values	take on any value in a range
Color	Blue	Green
Label vs Axis	Label Market(discrete)	Axis profit (continuous)
Color	Color Palette SUM(Sales - discrete)	Color Gradient SUM(Sales - continuous)
Color & Maps	A Dimension on color – "Symbol Map" A Measure on color – "Filled Map"	A Dimension on color – "Symbol Map" A Measure on color – "Filled Map"
Dates
Filtering	List	Range