loess3.plot: Loess plot for matched triplets.
In TriMatch: Propensity Score Matching of Non-Binary Treatments

This function will create a ggplot2 figure with propensity scores on the x-axis and the outcome on the y-axis. Three Loess regression lines will be plotted based upon the propensity scores from model. Since each model produces propensity scores for two of the three groups, the propensity score for the third group in each matched triplet will be the mean of the other two. If model is not specified, the default will be to use the model that estimates the propensity scores for the first two groups in the matching order.

loess3.plot(tmatch, outcome, model, ylab = "Outcome",
  plot.connections = FALSE, connections.color = "black",
  connections.alpha = 0.2, plot.points = geom_point, points.alpha = 0.1,
  points.palette = "Dark2", ...)

`tmatch`	the results of `trimatch`.
`outcome`	a vector representing the outcomes.
`model`	an integer between 1 and 3 indicating from which model the propensity scores will be used.
`ylab`	the label for the y-axis.
`plot.connections`	boolean indicating whether lines will be drawn connecting each matched triplet.
`connections.color`	the line color of connections.
`connections.alpha`	number between 0 and 1 representing the alpha levels for connection lines.
`plot.points`	a `ggplot2` function for plotting points. Usually `geom_point` or `geom_jitter`. If `NULL` no points will be drawn.
`points.alpha`	number between 0 and 1 representing the alpha level for the points.
`points.palette`	the color palette to use. See `scale_colour_brewer` and http://colorbrewer2.org/ for more information.
`...`	other parameters passed to `geom_smooth` and `stat_smooth`.