Feature Request: For DV vs PRED (and IPRED), add square option

[billdenney]

I prefer to see the x- and y-axes of my DV vs. IPRED and DV vs. PRED figures as square with equal ranges.

Would you consider adding an argument like square=TRUE (default FALSE to align with current practice), and if TRUE, it would add the following (which is the best way I know to get equal ranges and square axes):

  geom_blank(mapping=aes(x=DV, y=IPRED)) +
  coord_equal()

[bguiastr]

A while ago I had a discussion with @kestrel99 about this, I am rather against including more arguments to the main functions which after a while would be overloaded with options.

In my opinion this should be handled the ggplot2 way as nicely shown in your example but I am open to discussion :-)