`as.matrix.projection()` for GAMs: SDs for smoothing terms missing

[fweber144]

On branch develop (commit 96d8e11), this reprex:

options(mc.cores = parallel::detectCores(logical = FALSE))
data("kidiq", package = "rstanarm")
kidiq <- head(kidiq, 45)
fit_gauss <- rstanarm::stan_gamm4(
  kid_score ~ s(mom_iq),
  data = kidiq,
  iter = 500,
  seed = 734572
)

library(projpred)
prj <- project(fit_gauss, solution_terms = c("s(mom_iq)"),
               ndraws = 25)
colnames(as.matrix(prj))

gives

 [1] "b_Intercept"   "b_s(mom_iq).1" "b_s(mom_iq).2" "b_s(mom_iq).3"
 [5] "b_s(mom_iq).4" "b_s(mom_iq).5" "b_s(mom_iq).6" "b_s(mom_iq).7"
 [9] "b_s(mom_iq).8" "b_s(mom_iq).9" "sigma"

(so the output matrix does not include the SD(s) for the smoothing term) whereas

colnames(as.matrix(fit_gauss))

(correctly) gives

 [1] "(Intercept)"           "s(mom_iq).1"          
 [3] "s(mom_iq).2"           "s(mom_iq).3"          
 [5] "s(mom_iq).4"           "s(mom_iq).5"          
 [7] "s(mom_iq).6"           "s(mom_iq).7"          
 [9] "s(mom_iq).8"           "s(mom_iq).9"          
[11] "sigma"                 "smooth_sd[s(mom_iq)1]"
[13] "smooth_sd[s(mom_iq)2]"