library(ltm)
library(psych)
setwd("C:/Users/Admin/Desktop/IRT_CatSim")
irtdat<-read.csv("Fresh_r_2pl.csv",header=F)
head(irtdat)
PL2.rasch<-ltm(irtdat~z1)
summary(PL2.rasch)
plot(PL2.rasch,type=c("ICC"))
plot(PL2.rasch,type=c("IIC"))
Above is the code,When I run summary(PL2.rasch) I will get the following table
directly:
Coefficients:
value std.err z.vals
Dffclt.V1 3.1135 9.8208 0.3170
Dffclt.V2 -0.5157 0.8941 -0.5768
�
Discrm.V1 -1.3585 3.2062 -0.4237
Discrm.V1 -1.0032 8649.3103 -0.0001
�
Working on Item response theory and I�m struggling at calculating above values
manually.
You will get this difficulty and discrimination values directly, I just want
the simple formulas to calculate item difficulty and item discrimination.
Also how they have calculated theta(ability) and scores at the backend of the
code.
Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
________________________________
From: Richard O'Keefe <rao...@gmail.com>
Sent: Thursday, June 20, 2019 2:18:26 AM
To: shr...@outlook.com
Cc: r-help@r-project.org
Subject: Re: [R] Regarding R doubt
You did not say what your doubt about R was.
PL2.rasch has some class.
> class(PL2.rasch)
[1] 'Grofnigtz' # or whatever
The summary function is really just a dispatcher.
> summary.Grofnigtz
... a listing comes out here ...
Or you could look in the source code of whatever package you are usin.
On Thu, 20 Jun 2019 at 00:25, shr...@outlook.com<mailto:shr...@outlook.com>
<shr...@outlook.com<mailto:shr...@outlook.com>> wrote:
Hello Team,
I hope you are doing well.
I have one doubt about backend functioning of R command.
Currently I'm working on IRT analysis in python but this function is
implemented in R and in R they have direct rasch model library but no such
library in the Python.
So I wanted to know that is there any way to find the math or formula behind
the specific command of R language.
for eg, summary(PL2.rasch)
after this command you will directly get difficulty and discrimination values
like mentioned below:
Coefficients:
value std.err z.vals
Dffclt.V1 3.1135 9.8208 0.3170
Dffclt.V2 -0.5157 0.8941 -0.5768
Dffclt.V3 -1.3585 3.2062 -0.4237
Dffclt.V4 -1.0032 8649.3103 -0.0001
Dffclt.V5 0.0400 1350.8452 0.0000
So is there any way to find out the math behind this summary command ?
Thanks,
Shreepad
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