changing threshold can cause the UI to freeze

[diane]

For larger datasets, the length of time it takes to recompute the nway comparison can be non trivial. So if you increment through each threshold value it takes a long time to compute one, and then when it finishes starts to compute the next before the user can do anything.

Basically the nway recomputation needs to somehow be non-blocking.

[diane]

There's now a progress bar which gives the user the sense of that the app is doing something and isn't broken.

Though canceling would be nice.