Many thanks to all of you! AV plots are what I am trying to plot. Perhaps to reduce confusion I can give you an example of what I am doing:
I am looking at behaviour of re-sighted individuals over two time points. I use lm() on these data and obtain the residuals. Then I am interested to know whether an individuals' residual is related to a site fidelity mesure over the two time periods. Such that an individual that maintains a high degree of site fidelity shows less variation (has a smaller residual value) in (for example) aggressive behaviour. Therefore, using the absolute values of the residuals (as I am not interested in less or more aggressive) I plot these against the site fidelity measure to assess whether there is a correlation. The 1:1 relationship was to assess the deviation from 'absolute agreement', where the method above takes into consideration plasticity/noise between the two time periods. I hope this is a little clear and, although not a quote from the reviewer, this is essentially what was suggested. -- View this message in context: http://r.789695.n4.nabble.com/Force-regression-line-to-a-1-1-relationship-tp3809733p3815014.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.