Sorry for the unclear title.
The question I have is simple but difficult to articulate.
If I have the sample data set:

| Person | Date (m/d/y) | Weight |
| --- | --- | --- |
| Person1 | 01/15/21 | 93 |
| Person2 | 01/16/21 | 87 |
| Person3 | 01/14/21 | 73 |
| Person1 | 01/17/21 | 95 |
| Person2 | 01/15/21 | 85 |
| Person3 | 01/18/21 | 73.5 |

In R how do I find the average of Person1,2,3 weights. Keeping in mind I only their most recent weight is important.

Therefore, the correct answer should be:

* Person1 (01/17/21) weight = 95;
* Person2 (01/16/21) weight = 87;
* Person3 (01/18/21) weight = 73.5;

Mean = 85.2