Add cnorm() function?

[rpruim]

Long ago, this was #290. At that time we introduced cdist().

I had mostly forgotten about it, but today in class a student was complaining about having to convert probabilities from "central" to "tail" when it seemed clear that R could easily do this for her. While cdist() exists -- I had completely forgotten about it -- there is perhaps still a place for cnorm() which would look more like pnorm(), qnorm(), etc.

I suppose if I do this, I should do ct() as well.

[rpruim]

I've added both cnorm() and xcnorm().

library(mosaic)
cnorm(.95)
#>          lower    upper
#> [1,] -1.959964 1.959964
xcnorm(.95, mean = 100, sd = 10, alpha = 0.6)
#> 
#> If X ~ N(100, 10), then
#>  P(X <=  80.40036) = 0.025   P(X <= 119.59964) = 0.975
#>  P(X >   80.40036) = 0.975   P(X >  119.59964) = 0.025
#> 

#> [1]  80.40036 119.59964

Created on 2018-03-18 by the reprex package (v0.2.0).

[rpruim]

I've been experimenting with how to do these displays and I'm currently leaning to this instead. Among other things, this does a better job of making sure everything fits and tallies the probability for both tails together rather than separately.

library(mosaic)
options(digits = 3)
cnorm(.95)
#>      lower upper
#> [1,] -1.96  1.96
xcnorm(.95, mean = 100, sd = 10, alpha = 0.6)
#> 
#> If X ~ N(100, 10), then
#>  P(X <=  80.4) = 0.025   P(X <= 119.6) = 0.975
#>  P(X >   80.4) = 0.975   P(X >  119.6) = 0.025
#> 

#> [1]  80.4 119.6

Created on 2018-03-20 by the reprex package (v0.2.0).