as.ggplot() whithin functions shows error

[chagas98]

I wanted to code a simple function to check lm() and glm() models using the DHARMa package, which results in r-base plots. So I was using as.ggplot() to convert it into a ggplot object. This procedure worked well until I gathered a function like this:

check_models <- function(cm, modeltype) {

  if (modeltype == "lm"){
    
    qqres <-  ggplot(cm, aes(sample = rstudent(cm))) +
      geom_qq() + 
      stat_qq_line() +
      xlab("Theoretical Quantiles") +
      ylab("Studentized Residuals") +
      ggtitle("Q-Q Plot") +
      theme_bw()
    
    denres <- ggplot(cm) + 
      geom_density(aes(x = residuals(cm))) +
      xlab("Residuals") +
      ylab("Density") +
      ggtitle("Density") +
      theme_bw()
    return(qqres+denres)
    }

  if (modeltype == "glm"){

    cm_simres <- DHARMa::simulateResiduals(fittedModel = cm, n = 250)
    print(cm_simres)
    plot1 <- ggplotify::as.ggplot(~plot(cm_simres, asFactor = FALSE))
    
    cm_simres_refit <- DHARMa::simulateResiduals(fittedModel = cm,
                                                   n = 250,
                                                   refit = TRUE)
    plot2 <- ggplotify::as.ggplot(~DHARMa::testDispersion(cm))

    return(plot2) 
  }   

And got this error message:

Error in plot(cm_simres, asFactor = FALSE) : object 'cm_simres' not found

NOTE:

• cm is a model
• It showed the correct output in cm_simres when I rand the function with some lm() and "glm()
• when I removed ~ from plot1, I got this error: Error in UseMethod("as.grob") :
  no applicable method for 'as.grob' applied to an object of class "NULL"

I opened this issue because it is probably a ggplotfy problem, I tried to run fix() to find bugs, but It was tricky.

Thanks in advance for any help.

[GuangchuangYu]

see #11 (comment).