Update README.md

Author: arbennett

README.md

@@ -33,6 +33,7 @@ The structure of this repository is roughly as follows:
 - [Supplemental Example - Calculating Pi via Monte Carlo methods](https://arizona.box.com/s/73k40gl6pwz6vim887slrm5nmke2vlvh)
 - [Mon, Oct 7 - Geospatial data representations: vector data](https://arizona.zoom.us/rec/share/fzN7cHiQU7FkGBcbiAkXw0BXuioYGxmCh0-HPluATO7nbm1uytkV4bxdFsnbJmGe.El8jbclQpOU8tdgp)
 - [Mon, Oct 14 - Raster data & labeled arrays](https://arizona.zoom.us/rec/play/MdvXy5vaQ-4MPuAn8VNRwDzIwzXrLZsx62kp1kGBkzKxiG8GI2SJhPAyy3wpomrvS6pPogJbTOCzZy1n.4iTfdosXKJk8Xq2Y?canPlayFromShare=true&from=share_recording_detail&continueMode=true&componentName=rec-play&originRequestUrl=https%3A%2F%2Farizona.zoom.us%2Frec%2Fshare%2FfIEkIp79rYD5ic03Xr5ssmhBFIZefeAwOGmo1dHAUpczOlHDkceVrilQEF9TDKPF.IG_MEfjdVmAaI27E)
+- [Fri, Oct 18 - Groupby, resample, and rolling](https://arizona.zoom.us/rec/play/jTdRvW0MMNSOSNh1BSMGilSQP0d5jAoCJXTZmvoRAvcICpX9AeKSDsUYFoBiSyOkNM2xeC1rKZhOiBs0.qRAtiSxDVcmx5heo?canPlayFromShare=true&from=share_recording_detail&continueMode=true&componentName=rec-play&originRequestUrl=https%3A%2F%2Farizona.zoom.us%2Frec%2Fshare%2FS392SqlRkbp7EGyVf3aGqsF30TQHXwYtzUNY8ncr__E8W77OSWog78MydLn_zVF_.eYDAuAECHrlvcDQ_)
 
 ## Useful links
 Throughout the course we'll be amassing a lot of different resources that you can use.