geom_smooth doesn't work when function is entered with `::`

[IndrajeetPatil]

# loading needed libraries
library(ggplot2)
library(mgcv)
#> Loading required package: nlme
#> This is mgcv 1.8-24. For overview type 'help("mgcv-package")'.

# without `::`
ggplot(mtcars, aes(wt, mpg)) +
  geom_point() +
  geom_smooth(method = "gam", formula = y ~ s(x, k = 3))

# with `::`
ggplot(mtcars, aes(wt, mpg)) +
  geom_point() +
  geom_smooth(method = "gam", formula = y ~ mgcv::s(x, k = 3))
#> Warning: Computation failed in `stat_smooth()`:
#> invalid type (list) for variable 'mgcv::s(x, k = 3)'

# this indeed a function from `mgcv package`
args(mgcv::s)
#> function (..., k = -1, fx = FALSE, bs = "tp", m = NA, by = NA, 
#>     xt = NULL, id = NULL, sp = NULL, pc = NULL) 
#> NULL

Created on 2018-08-28 by the reprex package (v0.2.0.9000).

[clauswilke]

This is an mgcv bug. If you try to fit a gam model outside of ggplot2 you'll see that you'll get the same error. See #2621 for a prior discussion on this issue.

library(mgcv)
#> Loading required package: nlme
#> This is mgcv 1.8-24. For overview type 'help("mgcv-package")'.
x <- rnorm(50)
y <- x^2 + 0.3*rnorm(50)
df <- data.frame(x, y)
gam(y ~ s(x), data = df)
#> 
#> Family: gaussian 
#> Link function: identity 
#> 
#> Formula:
#> y ~ s(x)
#> 
#> Estimated degrees of freedom:
#> 5.22  total = 6.22 
#> 
#> GCV score: 0.05352554
gam(y ~ mgcv::s(x), data = df)
#> Error in model.frame.default(formula = y ~ mgcv::s(x), data = df, drop.unused.levels = TRUE): invalid type (list) for variable 'mgcv::s(x)'

Created on 2018-08-28 by the reprex package (v0.2.0).

[lock]

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