How to Work with Multiple Data Files

Introduction

In Q, you have the ability to analyze multiple data files in the same Q project file.  The project can refer to multiple data files at once. When a project has two or more data files, the following are available in Q:

• Multiple Variables and Questions tab; one for each data file.
• Multiple Data tabs; one for each data file.
• The ability to have tables and charts from different data files intermixed in the Outputs tab. 
• The ability to have a table/crosstab that simultaneously shows data from two different data files (read on to find out how to achieve this.)
• The ability to have a time series plot that simultaneously shows data from two different data files (read on to find out how to achieve this.)

Requirements

Two or more data sets that you want to load into the same Q project. 

• To create crosstabs from using questions from different data files, there must be a variable in both files which contains the same type of data (text, categorical, dates, etc.) and has some values which match from which to create a relationship between two files. 
• To create a time series chart using data from different data files, both files must contain a Date question with identical variable names and question names. 

Method

Adding Multiple Data Files

Once you have a project with one data set, use File > Data Sets > Add to Project again to add another file. You will then see the extra things listed above.

Crosstabbing Multiple Data Sources

Once you have a project with two data files, you have the ability to crosstab two questions from the separate data files. When you try and create crosstabs from questions in separate data files, you may be warned that you cannot crosstab questions from different data sources that do not have a relationship. To setup a relationship between the two data files select File > Data Sets > Relationships (see Edit Data File Relationships for more details). 

Once the relationship is setup, the sample size of a table will represent the number of respondents in the matched data.

If you wish to filter the table, and the relationship is Many-to-many, there must be a filter variable with the same Name and Label in both data files.

Charting a Time Series With Multiple Data Sources

Once you have a project with two data files, you have the ability to chart a time series that shows data from both data files.

The following prerequisites must be met:

• There must be a Date question in both data files with:
  • The same Variable Name
  • The same Question Name
  • The same Question Type (Date)
• If you wish to filter the Time Series chart, there must be a variable with the same Name and Label in both data files. The  tag must be turned on.
• If you wish to weight the Time Series chart, there must be a variable with the same Name and Label in both data files. The  tag must be turned on.

With the above prerequisites met, you may create a Time Series chart with multiple data sources by following these steps:

1. Click Create > Charts > Chart. 
2. Select Time series chart and click OK.
3. Set the brown dropdown at the bottom (the X axis) to the Date question that exists in both data files.
4. Set the first blue dropdown (the first Y axis) to a question from the first data file.
5. Set the second blue dropdown (the second Y axis, on the right) to a question from the second data file.
6. If you wish to filter or weight your data, select the variables in the filter and weight dropdowns.

Next

How to Create and Use Filters

How to Configure a Weight from Variable(s) in Q

How to Create a Time Series Graph