prior {catSurv} | R Documentation |
theta
Calculates the density at theta
of either the normal, Student's t, or uniform distribution.
prior(catObj, theta)
catObj |
An object of class |
theta |
A numeric value at which to evaluate the prior |
The priorName
slot of Cat
object needs to be either "UNIFORM"
, "NORMAL"
, or "STUDENT_T"
.
When priorName
slot is "NORMAL"
, the first element of priorParams
slot is the mean,
the second element is the standard deviation.
When priorName
slot is "STUDENT_T"
, the first
element of priorParams
slot is the non-centrality parameters and the second is degrees of freedom.
When priorName
slot is "UNIFORM"
, the elements of the priorParams
slot are the lower and upper bounds,
of the interval, respectively. Note that the "UNIFORM"
is only applicable for the expected a posteriori (EAP) estimation method.
The function prior
returns a numeric consisting of prior value, \pi(\theta)
, given the value \theta
.
This function is to allow users to access the internal functions of the package. During item selection, all calculations are done in compiled C++
code.
This function uses Boost C++
source libraries for the uniform and Student's t
distributions and calls dnorm4
written in C
which is identical to that
of dnorm
in R
.
Haley Acevedo, Ryden Butler, Josh W. Cutler, Matt Malis, Jacob M. Montgomery, Tom Wilkinson, Erin Rossiter, Min Hee Seo, Alex Weil
## Loading ltm Cat object
data(ltm_cat)
## Prior calculation for different distributions
ltm_cat@priorName <- "NORMAL"
ltm_cat@priorParams <- c(0, 1) ## Parameters are mean and standard deviation
prior(ltm_cat, theta = 1)
ltm_cat@priorName <- "STUDENT_T"
ltm_cat@priorParams <- c(1, 3) ## Parameters are non-centrality param and degrees of freedom
prior(ltm_cat, theta = 1)
ltm_cat@priorName <- "UNIFORM"
ltm_cat@priorParams <- c(-1, 1) ## Parameters are lower bound and upper bound of interval
prior(ltm_cat, theta = 1)