Plotting Heart Rate Change Over Time

Screenshots are not very useful, Can you please share a small part of the data set in a copy-paste friendly format?

In case you don't know how to do it, there are many options, which include:

  1. If you have stored the data set in some R object, dput function is very handy.

  2. In case the data set is in a spreadsheet, check out the datapasta package. Take a look at this link.

Ideally, to help us help you, you should prepare a reproducible example (reprex) illustrating your issue. Please have a look at this guide, to see how to create one: