I'm following up an old question addressed here:
calculate x-value of curve maximum of a smooth line in R and ggplot2
How could I calculate the Y-value of curve maximum?
Cheers
It would seem to me that code changes of "x" to "y" and 'vline' to 'hline' and "xintercept" to "yintercept" would be all that were needed:
gb <- ggplot_build(p1)
exact_y_value_of_the_curve_maximum <- gb$data[[1]]$y[which(diff(sign(diff(gb$data[[1]]$y)))==-2)+1]
p1 + geom_hline( yintercept =exact_y_value_of_the_curve_maximum)
exact_y_value_of_the_curve_maximum
I don't think I would call these "exact" since they are only numerical estimates. The other way to get that value would be
max(gb$data[[1]]$y)
As the $data element of that build-object can be examined:
> str(gb$data)
List of 2
$ :'data.frame': 80 obs. of 7 variables:
..$ x : num [1:80] 1 1.19 1.38 1.57 1.76 ...
..$ y : num [1:80] -123.3 -116.6 -109.9 -103.3 -96.6 ...
..$ ymin : num [1:80] -187 -177 -166 -156 -146 ...
..$ ymax : num [1:80] -59.4 -56.5 -53.5 -50.3 -46.9 ...
..$ se : num [1:80] 29.3 27.6 25.9 24.3 22.8 ...
..$ PANEL: int [1:80] 1 1 1 1 1 1 1 1 1 1 ...
..$ group: int [1:80] 1 1 1 1 1 1 1 1 1 1 ...
$ :'data.frame': 16 obs. of 4 variables:
..$ x : num [1:16] 1 2 3 4 5 6 7 8 9 10 ...
..$ y : num [1:16] -79.6 -84.7 -88.4 -74.1 -29.6 ...
..$ PANEL: int [1:16] 1 1 1 1 1 1 1 1 1 1 ...
..$ group: int [1:16] 1 1 1 1 1 1 1 1 1 1 ...