[Solved] Why do we use group = group in ggplot2 plots in R?

Question

The example that you give is for plotting maps, usually starting from a shapefile. In that case the data contains a column named group which is used by geom_polygon to ensure that boundaries and shapes are connected correctly. If the column were named something else, e.g. xxx, then you’d use group = xxx.

This question and answer demonstrate what happens when grouping is incorrect.

Accepted Answer

The example that you give is for plotting maps, usually starting from a shapefile. In that case the data contains a column named group which is used by geom_polygon to ensure that boundaries and shapes are connected correctly. If the column were named something else, e.g. xxx, then you’d use group = xxx.

This question and answer demonstrate what happens when grouping is incorrect.