Hi,
I want to add upper, lower and nominal line into the histogram without changing the Value field to contionous,
I added the test workbook and attached the screenshot for reference.
You can't do it accurately, because discrete values are equidistant categories along the axis, and if you're displaying 100 and 101 as categories, you can't plot a reference line at 100.2, any value you plot in that 'category' will be centred. That might be okay if you have a lot of values on the x-axis, where a pixel or 2 might be okay, but if your user zooms in to the chart, it's going to be clearly wrong. Another disadvantage is that at some point your discrete labels will become unreadable. What's your reason for not wanting to use a continuous axis?
With the discrete axis, you could try something like this:
which gives this output (x-axis squashed to fit the bars in):
versus continuous
