Author: Pedro J. Aphalo

Version 0.4.7 brings a fix for a bug that could prevent the use of weights passed through aesthetic weight in some of the model-fitting statistics. Several enhancements to the model fitting statistics make it easier to fit different models to different groups or panels, and make it possible/easier to select among methods supported by a model fit function.

Here is a simple example of fitting different models to different panels. Instead of using lm() as method, we define a wrapper function that tests for the significance of the slope in linear regression, and if not significant, fits the mean instead.

poly_or_mean <- function(formula, data, ...) {
   mf <- lm(formula = formula, data = data, ...)
   if (anova(mf)[["Pr(>F)"]][1] > 0.1) {
      lm(formula = y ~ 1, data = data, ...)
   } else {
      mf
   }
}

We pass the name of this function as argument to method overriding the default argument "lm".

ggplot(mpg, aes(displ, hwy)) +
   geom_point() +
   stat_poly_line(method = "poly_or_mean") +
   stat_poly_eq(method = poly_or_mean,
   aes(label = after_stat(eq.label)),
   label.x = "right") +
   theme(legend.position = "bottom") +
   facet_wrap(~class, ncol = 2)

Which produces the figure below, showing the mean in panels 2seater and minivan, and a linear regression in others.

Aditional examples are available in the free supplementary chapters of my book Learn R: As a Language.

Changes compared to version 0.4.6, the previous version in CRAN are:

• Fix bug in the handling of the weight aesthetic in some of the model fitting statistics.
• The model formula is in calls to stat_poly_eq() and stat_quant_eq() now retrieved from the returned fitted model object. This makes it possible model selection within the function passed as argument to method. (Inspired by an answer read in Stackoverflow.)
• Statistics now search for a matching function when an arbitrary name is supplied as a character string argument to parameter method.
• The character string passed as argument to parameter method is now parsed so that it can contain both the name of a model fit function and the argument to be passed to this function’s own method parameter. (Backward compatibility is maintained.)
• The stats that create equation labels now include a variable method in the returned data containing a character string with the method used in the model fit.

Documentation web site at http://docs.r4photobiology.info/ggpmisc/ includes all help pages, with output from all examples, vignettes as well as a changelog in HTML format.

NOTE: Version 0.4.7 is on its way to CRAN.

Please raise issues concerning bugs or enhancements to this package through GitHub https://github.com/aphalo/ggpmisc/issues