Scope_plot: Plot the score index 'index' as a function of arc length.

View source: R/Scope_plot.R

Scope_plotR Documentation

Plot the score index index as a function of arc length.


Arc length or scope is the distance along the space curved traced out as score index index increases from 0 to 100. It is measured in bits and is remains unchanged if the score index continuum is modified.


  Scope_plot(infoSurp, infoSurpvec, titlestr=NULL)



This is a positive real number indicating the total length of the space curve. It is expressed in terms of numbers of bits.


A vector of length 101 containing equally-spaced arc-length distances along the test information curve.


A string for the title of the data.


A gg or ggplot object defining the plot of infoSurp along the test information curve as a function of the score index index. This is displayed by the print command. The plot is automatically displayed as a side value even if no return object is specified in the calling statement.


Juan Li and James Ramsay


Ramsay, J. O., Li J. and Wiberg, M. (2020) Full information optimal scoring. Journal of Educational and Behavioral Statistics, 45, 297-315.

Ramsay, J. O., Li J. and Wiberg, M. (2020) Better rating scale scores with information-based psychometrics. Psych, 2, 347-360.

See Also



#  Example 1.  Display the arc length curve for the 
#  SweSAT multiple choice test with 24 items and 1000  examinees
infoSurpvec <- Quant_13B_problem_infoList$infoSurpvec
infoSurp    <- Quant_13B_problem_infoList$infoSurp
oldpar <- par(no.readonly=TRUE)
Scope_plot(infoSurp, infoSurpvec)

TestGardener documentation built on May 29, 2024, 3:31 a.m.