How to write name for label for a null value in the chart

[#1]

I am working on Finance dashboard. I got one null value for which I want to name the label as Undefined Number. How can I do it. 

[sunny_talwar]

On the front end, you can do like this:

If(Len(Trim(FieldName)) = 0, 'Undefined Number', FieldName)

[rittermd]

Currently you can't do anything in the visualization itself.  What Sunny suggested should work for you if you are not doing the calculation in the chart/table itself.

[#4]

[#5]

The undefined had the value but its field is not defined