R-vs-Python | repository contains several code examples comparing R

The issue is that when you draw a plot in base graphics draw directly on a device. The line of your code grob= plot(r_fit$unique.death.times, pred[1,], type = "l", col = "red") creates a NULL object (unlike ggplot which would return a plot object).

You can make the plot directly in ggplot (there are a few ways of doing this but I've done a simple example bolow) and convert it with ggplotly: