optical (version 1.7.1)

drawdesign: Graph for (optimal) design

Description

Generate plot for optimal design with four possible layouts. All layouts have design first incl. efficiency vs. random design; then line with item having minimal directional derivative

Usage

drawdesign(
  yyy,
  ip,
  ablim = 7,
  ylowl = -9999999,
  refline = 0.002,
  textout = TRUE,
  itemnum = NA,
  layout = 1,
  colvec = 1:12
)

Value

An optimal design plot is displayed.

Arguments

yyy

a optical object; the output of a call optical()

ip

matrix with item parameters for all items (number of rows determines number of items; number of column 2 (2PL) or 3 (3PL or mixed 2/3-PL with NA for 2PL-items in third column).

ablim

ability limits; plots will be made in the range [-ablim, ablim]

ylowl

y low level (minimum value of directional derivative shown in the plot)

refline

reference line correspond to desired minimum violation of equivalence theorem

textout

If textout=TRUE (default), the item parameters will be printed if number of items $<5$ and the efficiency vs. the random design; if textout=FALSE, no such text is printed

itemnum

number of items

layout

layouts of plots

• Layout 1: third panel has directional derivatives (cut at ylowl or lowest value of dirdev)

• Layout 2: third panel has violations of equivalence theorem, should be ideally small. Stopping criterion could be <0.002 (refline)

• Layout 3: third panel monitors efficiency of design vs. iteration number

• Layout 4: third panel monitors violations of equivalence theorem vs. iteration number

• Layout 5: third panel shows item characteristic curves

• Layout 0: only one panel with design

colvec

vector of color sequence for items (default is the R-default black, red, green, etc.)

See Also

convergenceplot

Examples

# 2PL-models for two items; parameters (a, b)=(1.6, -1) and (1.6, 1), respectively
ip <- cbind(c(1.6, 1.6),c(-1, 1))

yyy <- optical(ip)

drawdesign(yyy=yyy, ip=ip, ylowl=-1000, refline=0.002, layout=1)