Function to calculate the area under a selection of information curves
Compute the area within test or item information over a definite integral range.
areainfo( x, theta_lim, which.items = 1:extract.mirt(x, "nitems"), group = NULL, ... )
x |
an object of class 'SingleGroupClass', or an object of class 'MultipleGroupClass' if a suitable
|
theta_lim |
range of integration to be computed |
which.items |
an integer vector indicating which items to include in the expected information function. Default uses all possible items |
group |
group argument to pass to |
... |
additional arguments passed to |
a data.frame with the lower and upper integration range, the information area
within the range (Info), the information area over the range -10 to 10 (Total.Info), proportion
of total information given the integration range (Info.Proportion), and the number of items included (nitems)
Phil Chalmers rphilip.chalmers@gmail.com
Chalmers, R., P. (2012). mirt: A Multidimensional Item Response Theory Package for the R Environment. Journal of Statistical Software, 48(6), 1-29. doi: 10.18637/jss.v048.i06
dat <- expand.table(LSAT7)
mod <- mirt(dat, 1)
areainfo(mod, c(-2,0), which.items = 1) #item 1
## Not run:
areainfo(mod, c(-2,0), which.items = 1:3) #items 1 to 3
areainfo(mod, c(-2,0)) # all items (total test information)
# plot the area
area <- areainfo(mod, c(-2,0))
Theta <- matrix(seq(-3,3, length.out=1000))
info <- testinfo(mod, Theta)
plot(info ~ Theta, type = 'l')
pick <- Theta >= -2 & Theta <=0
polygon(c(-2, Theta[pick], 0), c(0, info[pick], 0), col='lightblue')
text(x = 2, y = 0.5, labels = paste("Total Information:", round(area$TotalInfo, 3),
"\n\nInformation in (-2, 0):", round(area$Info, 3),
paste("(", round(100 * area$Proportion, 2), "%)", sep = "")), cex = 1.2)
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.