Introduction to patterns

Patterns are a powerful tool, which have a number of uses in the Snap program.

In data entry, patterns are attached to a specific variable to:

• Ensure that respondents or data entry personnel enter the correct format for information such as postcodes, zip codes or National Insurance numbers. Snap looks for a similarity between what has been entered as the answer to a question and what has been specified as a possible match in the pattern.
• Convert the data into a standard form even if it has been entered in an unsuitable format, such as pound or dollar signs being included in quantity data.

In filters and derived variables, you can

• Use any of the defined patterns to temporarily change data, for example, converting literal text to lower case
• Use a pattern made up of several defined parts to select one of the parts (e.g. the area code in a phone number) and use that part to analyse the data.

You can use the Patterns already set up in Snap and create your own using the Patterns dialog from Tailor|Patterns.

The picture shows a pattern applied to q1a “Date of Visit” so that Snap only accepts dates in the DD/MM/YYYY format.

If the date is input in an incorrect format, an error message is displayed.

In this section Applying a pattern in the questionnaire window Applying a pattern in the Variables window Patterns during data entry Composition of a pattern Creating a new pattern example Testing a pattern Modifying, cloning and deleting patterns Copying patterns between surveys