Translations:Expression Manager/10/en

This image shows one way to review the relevance logic for a survey.  It computes Body Mass Index.  The relevance equation is shown in square bracket right after the variable name (which is in green).  So, the relevance of weight, weight_units, height and height_units are all 1, meaning that those questions are always asked.  However, the relevance for BMI is {!is_empty(height) and !is_empty(weight)}, which means that BMI will only be computed if the subject enters a value for both height and weight (thereby avoiding the risk of a divide by zero error).  Also, the Report question is only shown if the subject answers all four main questions (height, height_units, weight, weight_units).