dummy_expand {lazy.tools}

R Documentation

Dummmy Expantion of Categorical Data

Description

Dummmy Expantion of Categorical Data

Usage

dummy_expand(Uc, ncat = NULL, type = NULL, zero = 1)

Arguments

Uc	Item Response matrix in Compressed Format
ncat	a vector consisting of # of categories of each item
type	NOT used.
zero	= 0 to exclude the zero-th category from output

Details

In compressed format, Uc[i,j]=k means that subject i answers to item j by selecting option k, k=0,1,...,ncat[j].
This function expands this compressed format to uncompressed dummy expanded format:
That is, each item takes ncat[j] colums of U[, fromP[j]:toP[j]],
and the k+fromP[j]-th colum will be 1, and 0 elsewhere.

Value

A list of
U, ncat, type, zero, fromP, toP

Examples

# generate item response
# in uncompressed format
# set.seed(1701)
# res <- gendataIRT( 1, paramS1, npoints=7, thmin=-3, thmax=3 )
# U=res$U
# in compressed format
# set.seed(1701)
# res1 <- gendataIRT( 1, paramS1, npoints=7, thmin=-3, thmax=3, compress=1 )
# Uc=res1$U
#
# uncompressed data: ncat=c(2,2,4)
U <- "
Q1_0 Q1_1 Q2_0 Q2_1 Q3_0 Q3_1 Q3_2 Q3_3
1    0    1    0    1    0    0    0   
1    0    1    0    0    1    0    0   
1    0    1    0    1    0    0    0   
1    0    1    0    0    1    0    0   
1    0    0    1    0    0    1    0   
0    1    0    1    0    0    0    1   
0    1    0    1    0    0    0    1   
"; U=cards( U, header=1 )
#
# compressed data: ncat=c(2,2,4)
Uc <- "
 Q1 Q2 Q3
 0  0  0 
 0  0  1 
 0  0  0 
 0  0  1 
 0  1  2 
 1  1  3 
 1  1  3 
"; Uc=cards( Uc, header=1 )


# from compressed to uncompressed
U1=dummy_expand(Uc)$U
# back to compressed
Uc1=dummy_compress(U)$Uc
Print(U-U1)
Print(Uc-Uc1)

# zero=0 option
U2=dummy_expand(Uc, zero=0)$U
Uc2=dummy_compress(U2, zero=0, ncat=c(2,2,4))$Uc
Print(Uc-Uc2)

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