example of `{equate}` with SAT ACT data from `{psych}`

equate-sat-act.R

x <- psych::sat.act$ACT
y <- psych::sat.act$SATQ + psych::sat.act$SATV

ft <- equate::freqtab(data.frame(x, y))


eq0 <- equate::equate(
  x = ft,
  type   = "equipercentile",
  method = "none",         # single group
  smooth = "loglinear",
  degrees = list(4, 2, 2) # default list(4, 2, 2); maybe list(4, 2)
)

eq <- equate::equate(
  x = ft,
  type   = "equipercentile",
  method = "none",         # single group
  smooth = "loglinear",
  degrees = list(4, 2, 2), # default list(4, 2, 2); maybe list(4, 2)
  choose = TRUE,
  choosemethod = "aic",
  crit = eq0$concordance$yx,
  boot = TRUE,
  reps = 50
)

withr::with_par(list(mfrow = c(1, 3)), {
  # boring
  # plot(eq, addident = FALSE, out = "eqs", col = "blue")
  
  # combine everything
  con <- eq$concordance 
  boots <- eq$bootstraps
  
  plot(eq, xpoints = x, ypoints = y, addident = FALSE, col = "blue", addlegend = FALSE)
  
  # add estimate without bias
  lines(con$scale, con$yx - boots$bias, col = "red", lty = 1)
 
  # add se ranged
  lines(con$scale, con$yx + con$se.b, col = "green", lty = 2)
  lines(con$scale, con$yx - con$se.b, col = "green", lty = 2)

  # add rmse ranges
  lines(con$scale, con$yx + boots$rmse, col = "purple", lty = 3)
  lines(con$scale, con$yx - boots$rmse, col = "purple", lty = 3)
 
  # just bias  
  plot(eq, addident = FALSE, out = "bias", col = "red", addlegend = FALSE)
  abline(0, 0, lty = 2, col = "grey60")
  
  # se and rmse
  plot(eq, addident = FALSE, out = "se", col = "green", ylab = "SE | RMSE", addlegend = FALSE)
  plot(eq, addident = FALSE, out = "rmse", add = TRUE, col = "purple", lty = 2)
})