# [R] R coding errors

PROFESOR MADYA DR NORHAYATI BAHARUN norh@603 @end|ng |rom u|tm@edu@my
Fri Sep 8 04:22:35 CEST 2023

```Hi Sir,

STEPS TO MIX IRT_RMT APPROACH IN R

library(eRm)
library(ltm)
library(mirt)
library(psych)

str(HT)

response_columns <- HT[, 1:ncol(HT)]
response_matrix <- as.matrix(response_columns)

#3- Fit IRT model
irt_model <- gpcm(response_matrix)
irt_model
summary(irt_model)

#4- Fit Rasch model
rasch_model <- PCM(response_matrix)
rasch_model
summary(rasch_model)

#5- Compare item parameter estimates between IRT and Rasch models
irt_item_parameters <- coef(irt_model)
rasch_item_parameters <- coef(rasch_model)

#6- Compare person ability estimates between IRT and Rasch models
#TRY1
irt_person_abilities <- fscores(irt_model)                    ###ERROR###
#TRY2
#a(IRT)- Fit your GPCM model using ltm
irt_model <- gpcm(data = HT, constraint = "1PL")

#a(IRT)- Calculate factor scores (IRT person abilities)
irt_person_abilities <- factor.scores(irt_model)             ###ERROR###
irt_person_abilities_dim1 <- factor.scores(gpcm_model, f = 1)

#TRY3
# Fit your GPCM model using mirt
irt_model <- mirt(data = HT, model = "gpcm", itemtype = "graded")
###ERROR###

# Calculate factor scores for dimension 1 (adjust the dimension as needed)
irt_person_abilities_dim1 <- fscores(gpcm_model, method = "EAP", dims = 1)

#b(RMT)
rasch_person_abilities <- person.parameter(rasch_model)\$theta

#7- Perform model comparison using fit statistics (e.g., AIC, BIC)
irt_aic <- AIC(irt_model)
rasch_aic <- AIC(rasch_model)

irt_bic <- BIC(irt_model)
rasch_bic <- BIC(rasch_model)

#8- Print or visualize the results for comparison
print("Item Parameter Estimates:")
print(irt_item_parameters)
print(rasch_item_parameters)

print("Person Ability Estimates:")
print(irt_person_abilities)                                  ###ERROR###
print(rasch_person_abilities)

print("Model Fit Statistics:")
print(paste("IRT AIC:", irt_aic))
print(paste("Rasch AIC:", rasch_aic))

print(paste("IRT BIC:", irt_bic))
print(paste("Rasch BIC:", rasch_bic))

Many thanks.

Regards,

Norhayati

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