Code below fails when I add the filter line – any ideas? ‘Dt’ is a variable.

 viz.data(data)                                                      // Expects hierarchical array of objects.
        .width(600)                                                     // Width of component
        .height(600)                                                    // Height of component
        .children(function (d) { return d.values })                     // Denotes the property that holds child object array
        .key(function (d) { return d.id })                              // Unique key
        .value(function (d) {
            return Number(d["agg_" + valueField]) })                    // The property of the datum that will be used for the branch and node size
        .fixedSpan(-1)                                                  // fixedSpan > 0 will use this pixel value for horizontal spread versus auto size based on viz width
        .branchPadding(.07)
        .filter(function (d) { return d.Dept== Dt;})
        .label(function (d) {                            
        	            // returns label for each node.
            return trimLabel(d.key)})
        .on("measure",onMeasure)                                        // Make any measurement changes
        .on("mouseover",onMouseOver)                                    // mouseover callback - all viz components issue these events
        .on("mouseout",onMouseOut)                                      // mouseout callback - all viz components issue these events
        .on("click",onClick);