I'm calculating absolute relative error at the moment for a practical I did. However, I've hit a brick when attempting to find a general relative error I can use because I need to gradient to find something else which also requires a relative error calculation. I have frequency (+/- 0.0005) graphed against stopping potential (+/- 0..000005) and obviously because both of them differ, the relative percentages are very different. How do I find the general absolute relative error from a gradient. I'm sorry if I didn't explain it that well but I can't think of a better way to convey what I'm trying to say.