Used the well known wizard to create the set analy
// ---------------------------------------------------------------------
// Calculate the Sum of "calDueDate"
// based on all values
// ~~
// but before calculating
// - Select records in field "Month(calDueDate)" matching the condition: [equal to "Month(Today())"]
// ~~~~
// Created by http://tools.qlikblog.at/SetAnalysisWizard/
// ---------------------------------------------------------------------
=Sum({1<Month(calDueDate)={$(=Month(Today()))}>}calDueDate)
However using in my chart does not return any data
Other values in use in the same chart work but I am specifying the item in those case for example :
Sum({1 <DueDateFinYear = {'2012/13'}>} i_lifts) ---- Different field of course
