I am trying to make plots scatter-graph to represent maximum and minimum x and y values for various sources E.g. Algae= d13 has -5 >= C >= -10 and 5 <= C/N <= 9.

As shown in the image the plots form a box but I need to filter out the sources to construct lines between them separately. I tried using the filter function but had no luck, I've only been using R for a week or so...