Is your feature request related to a problem? Please describe.

I noticed it isn’t possible to set the uncertainty to zero for any of the variables. For example, I get an error if I use a normal distribution with sigma=0 for row shading loss.

Describe the solution you'd like

It would be nice to have a checkbox to enable/disable one or more variables for the uncertainty analysis, or to be able to set them to zero, but I think the checkbox would be preferred.

A comment from @cpaulgilman in our email exchange: "I think a good way to implement that would be as you suggest... as a check box so you can turn off a distribution without losing its settings and then turn it back on."

Describe alternatives you've considered

It seems that the only option is to make the uncertainty ranges very very small.

Additional context

Here's a mock-up of what I have in mind: