Plots > Working with Plots > About Units and Complex Numbers in Plots
  
About Units and Complex Numbers in Plots
Plots in PTC Mathcad accept units but they do not accept complex numbers.
Units
When an axis expression contains units, the corresponding base units are displayed in the unit placeholder of the axis expression. You can convert the base units into other units as you do for results in math expressions. You can also add a scaling factor in the unit placeholder to zoom in or out of the plot.
Complex Numbers
PTC Mathcad does not plot points that have an imaginary part. To plot the real or imaginary part of a point, use the Re and Im functions.