Solution_09.R

# Exercise 9

# let's use the previous solution
source("Solution_08.R")

# create a directory to store plots in, if it doesn't exist
if (!dir.exists("plots")) dir.create("plots")


# we now want to save all of the files that were created previously.
# for this, we need a combination of the plots, and filenames.

# we can use the names assinged to the list items of the plots object
names(plots)

# we need to append the names with ".png"
# (hint: use the paste0 function for string concatenation in R)

filenames <- paste0(names(plots), ".png")

# now, we can use the walk2 function, along with the filenames and plots objects
# and the ggsave function.

# we don't need to assign the output of walk2 to a variable: walk is for function
# side effects and only returns the first input

# make sure to set the following arguments with ggsave:
#   device = "png"
#   path = "plots"
# you could also play about with the height/width by using the following arguments
#   width = 20
#   height = 12
#   units = "cm"
# if you have the Cairo package installed, then I would recommend adding in
#   type = "cairo-png"
#   dpi = "retina"
# (try running those lines, if they don't work then install.packages("Cairo").
#  this will produce much higher quality graphics that are anti-aliased)

walk2(filenames,
      plots,
      ggsave,
      device = "png",
      path = "plots",
      type = "cairo-png",
      dpi = "retina")