Plotting Equating Results
Description
Functions for plotting equating functions from one or more objects
of class “equate
” or “equate.list
”.
Usage
1 2 3 4 5 6 7 8 9  ## S3 method for class 'equate'
plot(..., elist = NULL, add = FALSE, out = "eqs",
xpoints, ypoints, addident = TRUE, identy, identcol = 1, rescale = c(0,
1), xlab = "Total Score", ylab, col = rainbow(length(x)), pch, lty = 1,
lwd = 1, subset, morepars = NULL, addlegend = TRUE, legendtext,
legendplace = "bottomright")
## S3 method for class 'equate.list'
plot(x, ...)

Arguments
... 
one or more equating objects, each containing results for equating the same two test forms. 
elist 
list of equatings to be plotted. 
add 
logical, with default 
out 
character vector specifying the output to be plotted, either
equating functions ( 
xpoints, ypoints 
optional vectors of the same length containing raw scores on forms X and Y, assuming a single group or equivalent groups design. 
addident 
logical, with default 
identy 
vector of y coordinates for plotting the identity line.
Defaults to the X scale when 
identcol 
color used for plotting the identity line. 
rescale 
intercept and slope, with default 0 and 1, used to rescale all lines before plotting. 
xlab, ylab, col, pch, lty, lwd 
graphical parameters passed to 
subset 
vector for subsetting the output when multiple equating
functions are included in 
morepars 
list of additional graphical parameters, excluding

addlegend 
logical, with default 
legendtext 
character vector of text to be passed to the 
legendplace 
placement of the legend. 
x 
“ 
Details
Equating functions (out = "eqs"
) are plotted as lines based on
the concordance table for each equating object that is supplied. Standard
errors (out = "se"
) default to bootstrap standard errors, if
available, otherwise, analyitical standard errors are plotted. Bias
(out = "bias"
) and RMSE (out = "rmse"
) are also taken
from bootstrapping output.
Examples
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15  # See ?equate for additional examples
rx < as.freqtab(ACTmath[, 1:2])
ry < as.freqtab(ACTmath[, c(1, 3)])
set.seed(2007)
req1 < equate(rx, ry, type = "i", boot = TRUE, reps = 5)
req2 < equate(rx, ry, type = "m", boot = TRUE, reps = 5)
req3 < equate(rx, ry, type = "l", boot = TRUE, reps = 5)
req4 < equate(rx, ry, type = "e", boot = TRUE, reps = 5,
smooth = "loglin", degree = 3)
req5 < composite(list(req1, req2), wc = .5, symmetric = TRUE)
plot(req1, req2, req3, req4, req5[[1]], addident = FALSE)
plot(req5)
