Introduction
Version 1.2 of the WrightMap package allows you to directly access the functions used for drawing the person and item sides of the map in order to allow more flexible item person maps. The parts can be put together on the same plot using the split.screen function.
Calling the functions
Let’s start by installing the latest version of the package from CRAN.
install.packages('WrightMap')
library(WrightMap)And set up some item data.
items.loc We can draw a simple item map by calling one of the item side functions. Currently there are three: itemModern, itemClassic, and itemHist.
The itemModern function is the default called by wrightMap.
itemModern(thresholds) The itemClassic function creates item sides inspired by text-based Wright Maps.
itemClassic(thresholds)
Finally, the itemHist function plots the items as a histogram.
itemHist(thresholds)
Similarly, the person side functions allow you to graph the person parameters. There are two, personHist and personDens.
## Mock results
multi.proficiency personHist(multi.proficiency)
personDens(multi.proficiency)
To use these plots in a Wright Map, use the item.side and person.side parameters.
wrightMap(multi.proficiency,thresholds,item.side = itemClassic,person.side = personDens)
Use with CQmodel: The personData and itemData functions
The person side and item side functions are expecting data in the form of matrices. They do not recognize CQmodel objects. When a CQModel object is sent to wrightMap, it first extracts the necessary data, and then sends the data to the plotting functions. In 1.2, the data processing functions have also been made directly accessible to users in the form of the personData and itemData functions. These are fast ways to pull the data out of a CQmodel object in such a way that it is ready to be sent to wrightMap or any of the item and person plotting functions.
The personData function is very simple. It can take either a CQmodel object …read more
Source:: r-bloggers.com