Can I use published data by other authors in my study? I'm in the process of publishing an article in the Engineering field. The manuscript got a preliminary acceptance, and should be published after few modifications. However, based on one comment I got, I need to evaluate my model's performance based on certain input data. I don't have such data, but such data has been published before in the literature. Is it OK to use the date published by other authors just to evaluate my model?
What am I going to do is to digitize the published figures and use the values. I'm going to cite the papers, but I'm not going to add the figures or the datapoints to my manuscript.
Yeah, it is fine.  If anything, it is how the literature and scientific enterprise is supposed to work.  I would just be clear about attribution and that you haven't discovered the relationship (from first paper) but instead used existing info to validate your method.