Auto: lineplot add 0 line
individual line plots: add a horizontal line at 0 to visually split pos & neg absolute values of marginal effect? currently Y scale tied to values, which gives impression that max marginal effect is 'big' but all might be tiny option to ALSO plot in log scale +/- with coloured shaded areas for rule-of-thumb better to worse? More to less?
@2023-05-18 L824 & 884
abline(h = 0) # https://github.com/SimonDedman/gbm.auto/issues/7
check col lty lwd
not working for some reason, dismo weirdness? see this.
if making my own gbm.plot.sd, also see this
Could also add a vertical abline(s) where the data crosses the 0 lines?
Could get around the issue by (optionally) adding an additional series of data ranging from min to max x, with all y's as 0, then plotting that?