Mastering Variables in QlikView for Dynamic Data Storytelling

Introduction

If you‘re a QlikView developer looking to take your applications to the next level, mastering the use of variables is essential. Variables allow you to store values and expressions to be reused throughout your application, enabling more dynamic, automated behaviors and richer interactivity. They are the key to transforming static dashboards into data-driven stories that guide the user experience.

In this expert guide, we‘ll dive deep into the world of QlikView variables, with a special focus on applying them in conditional expressions. Whether you‘re new to variables or looking to optimize your usage, you‘ll gain practical tips and hands-on examples you can put into action immediately.

Understanding QlikView Variables

At their core, variables in QlikView serve two main purposes:

1. Storing a static value that you want to reuse across your application
2. Containing a calculated expression that can be dynamically evaluated

By referencing a variable instead of hard-coding a value or formula in multiple places, you make your application more maintainable. If you need to update the value or logic later, you only need to change it in one place – the variable definition.

Variables also enable you to create more generic, reusable logic. For example, instead of writing filters that are specific to a field value, you can store the value in a variable and reference the variable in your filters. Then you can easily change or automate the value as needed.

Creating Variables

There are a few different ways to create variables in QlikView. The simplest is using the Variable Overview dialog (found under Settings in the menu). Here you can create a new variable, give it a name, and assign it a static value or expression.

Another common method is using the SET and LET statements in the script editor:

// Static variable
SET vCurrentYear = 2023; 

// Expression variable
LET vSalesTarget = Sum(Sales) * 1.15;

The difference is that SET will treat the value as a literal string, while LET will evaluate it as an expression. In general, you should use LET for calculated variables.

It‘s a good practice to follow a naming convention to keep your variables organized, such as prefixing with "v" for static value variables and "e" for expression variables.

Using Variables

Once you‘ve defined a variable, you can easily reference it by name throughout QlikView. For static value variables, you can use it as-is. For expression variables, you need to use the $() syntax to evaluate it:

// Reference static variable
If (Year <= $(vCurrentYear), ‘Current‘, ‘Future‘)

// Evaluate expression variable 
$(eSalesTarget)

Remember that if you defined the variable using LET, you don‘t necessarily need the $() when referencing it in an expression. But using it consistently makes your code more readable.

Variables can be used practically anywhere in QlikView you would use a value or expression, including:

• Chart dimensions and measures
• Expressions and labels
• Show conditions
• Calculated dimensions and fields
• Script logic

We‘ll explore more specific applications later in this guide. The key is to look for opportunities to replace hard-coded or repetitive values with variables to make your application more flexible and automated.

Variables in Action: Conditional Expressions

One of the most powerful applications of QlikView variables is in conditional expressions. By storing conditions or thresholds in variables, you can dynamically change the behavior and appearance of your application based on the current data and user inputs.

Let‘s look at a practical example. Say you have a KPI dashboard that shows sales performance by region. You want to highlight regions that are behind pace in red, and those ahead of target in green. You could hard-code the thresholds, but then you‘d have to manually update them each year as targets change.

A better approach is to store the target thresholds in variables:

LET vRedThreshold = Sum(SalesTarget) * 0.9;
LET vGreenThreshold = Sum(SalesTarget) * 1.1; 

Then, in your KPI object, you can use a conditional expression to set the background color:

If( 
  Sum(Sales) < $(vRedThreshold),
  ‘red‘,
  If( 
    Sum(Sales) > $(vGreenThreshold),
    ‘green‘,
    ‘lightgray‘
  )
)

Now the thresholds will automatically update based on the current data and selections. If you need to adjust them, you can simply change the variable expressions.

Showing/Hiding Objects Conditionally

Another common use case for conditional variables is showing and hiding objects based on user selections or data conditions. For instance, you might have a detailed breakdown that‘s only relevant when a single region is selected.

To implement this, first create a variable to store the condition:

LET vShowDetail = GetSelectedCount(Region) = 1;

Then, in the object‘s Show Condition property, reference the variable:

$(vShowDetail)  

Now the object will only display when exactly one region is selected. You can get creative with this concept and create variables to control the visibility of entire sections or sheets based on user preferences or data-driven conditions.

Conditional Formatting and Styles

Variables can also be used to conditionally apply formatting and styles to your objects. Let‘s say you want to display a custom icon in a table depending on the sales performance:

LET vIconExpression = If(Sum(Sales) < $(vRedThreshold), ‘warning.png‘, ‘check.png‘);

Then in the table, you can reference the variable in an image expression:

$(vIconExpression)

This will display the appropriate icon based on the current sales data. You can extend this concept to conditionally format text, colors, and other visual properties to guide users‘ attention to what‘s most important.

Advanced Variable Techniques

As you get more comfortable with variables, you can start to leverage them in more advanced expressions and scripting. Here are a few examples:

Set Analysis with Variables

In set analysis, you can use variables to store complex search conditions or modifiers. For example:

LET vCurrYearFilter = {<Year={$(vCurrentYear)}>};

Sum(Sales) / Sum({$(vCurrYearFilter)} Sales)

This expression calculates the share of sales for the current year. By storing the year filter in a variable, you can easily reuse it in multiple places and update it centrally.

Dynamic Script Logic

Variables can also enable more dynamic script logic. For instance, you could store a file path in a variable and use it in your load statements:

LET vDataFile = ‘C:\Data\Sales.qvd‘;

LOAD * FROM $(vDataFile);

This makes it easy to change the data source without modifying the load statement itself. You can even prompt the user for the file path using an input box and store it in the variable.

Optimizing Complex Conditionals

When you have complex conditional logic with many nested If() statements, it can start to impact performance. One optimization technique is to evaluate the sub-conditions in variables first:

LET vCondition1 = Sum(Sales) > 1000000;
LET vCondition2 = Count(distinct CustomerID) > 100;

If( $(vCondition1) and $(vCondition2), ‘Segment A‘, ‘Segment B‘)

By breaking out the conditions, you make the final expression more readable and performant.

Tips for Effective Variable Management

As you start to rely more on variables in your QlikView applications, it‘s important to establish some best practices to keep things organized and maintainable:

1. Use a consistent naming convention and add comments to describe what each variable represents
2. Group related variables together using a prefix or suffix (e.g. vFilter_* for all filter variables)
3. Regularly audit your variables and remove any that are no longer being used
4. Test your variable expressions thoroughly, especially when using complex conditionals
5. Consider creating a variables overview sheet in your application for documentation and user reference
6. Use variables judiciously – don‘t go overboard creating variables for every single value

By following these guidelines, you‘ll be able to leverage variables effectively to create dynamic, data-driven stories in QlikView without adding unnecessary complexity.

Conclusion

Variables are a critical tool in the QlikView developer‘s toolkit, enabling richer interactivity, dynamic behavior, and more maintainable applications. By mastering variables, especially in conditional expressions, you can transform your dashboards from static reports into interactive data stories that engage and inform your audience.

The key is to start thinking about every hard-coded value or repetitive expression in your app as an opportunity to use a variable instead. Look for ways to parameterize your logic to make it more flexible and reusable. And don‘t be afraid to experiment with creative applications of variables to make your apps more user-friendly and automated.

With the techniques and best practices covered in this guide, you‘re well on your way to becoming a variable virtuoso. So go forth and create some truly compelling, dynamic data stories in QlikView! And if you get stuck, don‘t forget to consult the QlikView community forums and online resources for help and inspiration.