Is it possible to plot the smooth components of a gam fit with ggplot2?

Question

I am fitting a model using gam from the mgcv package and store the result in model and so far I have been looking at the smooth components

Answer 1

Updated to allow user to choose which variables are plotted. Changed 'residuals' term to 'res_data' to avoid conflict with residuals function.

ggplot.model <- function(model, type="conditional", res=FALSE, 
                       col.line="#7fc97f", col.point="#beaed4", size.line=1, size.point=1, no_col = NULL,
                       what = "all") {
  require(visreg)
  require(plyr)
  
  plotdata <- visreg(model, type = type, plot = FALSE)
  smooths <- ldply(plotdata, function(part)   
    data.frame(Variable = part$meta$x, 
             x=part$fit[[part$meta$x]], 
             smooth=part$fit$visregFit, 
             lower=part$fit$visregLwr, 
             upper=part$fit$visregUpr))
  res_data <- ldply(plotdata, function(part)
    data.frame(Variable = part$meta$x, 
               x=part$res[[part$meta$x]], 
               y=part$res$visregRes))
  
   if (what != "all") {
    smooths <- smooths %>%
      filter(lapply(Variable,as.character)%in% what)
    res_data <- res_data%>%
      filter(lapply(Variable,as.character)%in% what)
   }
  
  
  if (res)
    ggplot(smooths, aes(x, smooth)) + geom_line(col=col.line, size=size.line) +
      geom_line(aes(y=lower), linetype="dashed", col=col.line, size=size.line) +
      geom_line(aes(y=upper), linetype="dashed", col=col.line, size=size.line) +
      geom_point(data = res_data, aes(x, y), col=col.point, size=size.point) +
      facet_wrap(. ~ Variable, scales = "free_x", ncol = no_col) + theme_bw()
  else
    ggplot(smooths, aes(x, smooth)) + geom_line(col=col.line, size=size.line) +
      geom_line(aes(y=lower), linetype="dashed", col=col.line, size=size.line) +
      geom_line(aes(y=upper), linetype="dashed", col=col.line, size=size.line) +
      facet_wrap(. ~ Variable, scales = "free_x", ncol=no_col)
}