Improving graphs presentations
One of the easiest way to improve graphs presentation is by changing the characters of the point data. You can do it by using pch parameter that sets “an integer specifying a symbol or a single character to be used as the default in plotting points” in the graphic command you are using. Altering the pch values will prompt different symbols representing your points in the graph. Follow a picture with the corresponding values of respective symbles:
Thus in a plot command you can specify the values of pch that best fit to your intends. For example if I want to use a filled circle I can do:
Play with the possibilities and enjoy!