R Notebook

So we want to add person-level summaries of a variable to the right of a data-frame?

1. Create some data

2. The dplyr way

3. The data.table way

4. The base R way

ID	X	x
1	-0.5811347	0.2034073
1	-0.3858843	0.2034073
1	0.9627655	0.2034073
1	1.6026897	0.2034073
1	-0.5813995	0.2034073
2	0.6804060	-1.0253115