Writes a file of commands for the dot program to draw a graph
proposed by Rosenbaum (1987)
and useful for checking for non-intersecting
item characteristic curves which are a property of various
sorts of latent scale including Guttman, Rasch and the Mokken
double monotone scale.
Usage
draw.latent(mat, rootname = NULL, threshold = 0, which.npos = NULL,
labels = NULL, reorder = TRUE)
## S3 method for class 'draw.latent'
print(x, ...)
## S3 method for class 'draw.latent'
plot(x, graphtype = "png", ...)
Arguments
mat
A matrix or data.frame of binary item responses
rootname
The commands will be written to rootname.dt.
If NULL they will be written
to the standard output
threshold
Patterns are only printed if more frequent than threshold,
defaults to 0 meaning all those which actually occur are printed
which.npos
Which values of number of items positive to print,
NULL means all and is the default. Duplicates are removed
labels
Labels for subgraphs, NULL means none, a character
vector supplies the labels, otherwise labelled as n positive
reorder
logical, put the items in ascending order of prevalence,
defaults to TRUE
x
An object of class draw.latent
graphtype
Character: one of the graph types supported by dot
...
Other arguments
Details
The plot method actually does the plotting and invisibly
returns the result of the system command which executes dot.
The output file will be named with the rootname followed
by the graph type (after a dot).
The print method prints some details.
The routine does not draw the graph itself but leaves that
to the dot program from graphviz which you need
to install.
More extensive documentation is provided in the
documentation directory.
Value
Outputs the commands to
draw the patterns and in addition returns:
rootname
the rootname for the command file
which.npos
which values of items positive were printed. Differs
from input parameter if for some there were no valid
patterns to print or duplicates have been
removed
new.order
order of original items from left to right in displayed
diagram.
If new.order==TRUE new.order[i] is the index in the original dataset
of the $i$th item in increasing prevalence
Author(s)
Michael Dewey
References
P R Rosenbaum.
Probability inqualities for latent scales.
British Journal of Mathematical and Statistical Psychology,
40: 157–168, 1987