A Gentle Introduction to Data Cleaning

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Introduction
In this section, learn about the “horror stories” of where data errors in spreadsheets have led to real consequences and how you can avoid them yourself.
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- 1.1
  Course Outline
Section 1: Nuts and chewing gum
In this section, you’ll gain practical knowledge of common formatting and layout features of spreadsheets and some ideas about how to present your raw data to others so they will love you!
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Section 2: The Invisible Man is in your spreadsheet, messing with your data
In this section, you’ll learn how even characters which you cannot see can cause havoc in data analysis. The section will teach you to ghostbust white space and other non-printable characters such as carriage returns, spaces and tabs. Once you have removed them, you can get on with your analysis in peace.
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Section 3: Your data is a witch’s brew
Three is not a number. Nor is a million. At least not when they are typed in as text in a cell in a spreadsheet. Your spreadsheet is pedantic and needs everything to be precise and consistent. Read on to learn more.
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Section 4: Did you bring the wrong suitcase (again)?
All our spreadsheet wants from us is each cell of data to be organised and neatly packed. In this section, you will analyse data to highlight problems in the way it has been structured so as to avoid them in your own work with data.
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Reading list

Here’s a detailed run through of the different basic number formats that are available in Excel.
These basic practical spreadsheet skills are useful in exploring and testing out the data:
- Adding up a column of numbers, using Google Spreadsheet as an example
- Sorting data, using Google Spreadsheet as an example
- Here’s how to apply auto-filter in Excel.
- The sort and filter course in data fundamentals.
Many people find problems with data types when they start using forms of numbers that are very particular, such as organisational reference numbers, like social security or national identity numbers, telephone numbers, locational information like latitude and longitude. Spreadsheets can build “Custom number formats”. Here’s some reading about them.
- A simple example from TechRepublic of how custom number formats solve annoying problems in spreadsheets.
- A detailed note about how custom number formats work, by Ozgrid.
- A nicely put together reference for common custom number formats in Excel, by Simon Page.

Some work