sig.region: Johnson-Neyman Significance Regions
In ngreifer/modprobe: Moderation Probing Tools

Estimates the Johnson-Neyman significance bounds for a linear fit. These are the bounds at which the effect of the predictor on the outcome changes from being significant to being non-signficant given varying values of the moderator(s). Also estmates the confidence bands for the slope of the predictor on the outcome for varying levels of the moderator(s).

1	sig.region(fit, predictor = NULL, moderator = NULL, mod.range = NULL, at.mod2.level = NULL, mod2.level.names = NULL, alpha = 0.05, simultaneous = FALSE)

`fit`	the output of a call to `lm()` containing a linear interaction between a continuous predictor and one or two moderators. If other variables are included in the model, all output will be taken with those variables set to 0.
`predictor`	optional; a string containing the name of the predictor. By default, it is assumed that the first variable to appear in fit is the predictor; if not, it must be specified here.
`moderator`	optional; a string containing the name of the moderator. By default, it is assumed that the second variable to appear in fit is the sole moderator; if not, it must be specified here. If more than one moderator is present, all of them must be named because the default is to only use the second variable in the fit.
`mod.range`	optional; a vector of length 2 containing the range of the first moderator for which the simple regression lines are to be plotted in a call to `plot.sig.region()`. The output of `sig.region()` will also note whether the computed significance bounds are within the range of the moderator. If `NULL`, will use the range of the moderator given in `fit`.
`at.mod2.level`	optional; a list of values of the second moderator (if present) for which the signfiicance bounds and regions are to be computed. If `NULL` and two moderators are specified, will compute the signfiicance bounds and regions at the mean, mean - SD, and mean + SD of the second moderator. Ideally, each item in the list will be named in accordance with each moderator, but otherwise each item will be used in the order it appears.
`mod2.level.names`	optional; a vector of the same length as `at.mod2.level` containing the names of the levels of the second moderator for which the signfiicance bounds and regions are to be calculated, in the same order as `at.mod2.level`. If `NULL`, will use the values of the second moderator as the names, unless `at.mod2.level` is also `NULL` and the moderator is continuous, in which case "Mean", "Mean - SD", and "Mean + SD" will be used.
`alpha`	the alpha value (significance criterion) corresponding to the confidence level for the signfiicance bounds and regions.
`simultaneous`	whether the bounds and bands should be calculated considering the tests as simultaneous or not. If so, a stricter criterion is used, making the bands wider.
`sr`	a `sig.region` object; the output of a call to `sig.region()`.
`digits`	the number of digits to be displayed for the significance bounds.
`colors`	a vector of colors to be used to specify the colors of the lines in the significance bands plot. See 'Color Specification' at `par`.
`ggplot2`	logical; whether to print results using ggplot2 or R's graphics.