# draw.latent {latdiag}

### Description

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.

### Values

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

### References

P R Rosenbaum. Probability inqualities for latent scales. *British Journal of Mathematical and Statistical Psychology*, **40**: 157--168, 1987

### Examples

##---- Should be DIRECTLY executable !! ---- library(ltm) res <- draw.latent(LSAT, rootname = "lsat") # # now need to plot(res, graphtype = "png") #

Documentation reproduced from package latdiag, version 0.2. License: GPL-2