samediff: Create Discrimination Probabilities (Psi) from Data Frame

Description Usage Arguments Details Value See Also Examples

Description

Creates matrices with discrimination probabilities, number of trials, number of different answers, and stimulus intensities from a data frame.

Usage

1
psi(data, oa1 = "s1", oa2 = "s2", resp = "resp")

Arguments

data

data frame with repeated same-different judgments.

oa1, oa2

name of the variable that contains the stimulus intensities in the first and second observation area.

resp

name of response variable for same-different judgments; answers have to be d and s for "different" and "same" response, respectively.

Details

The data frame must include at least a column for the response and one column each for observation areas one and two. The return value of psi may serve as an input to qdm that fits a quadrilateral dissimilarity model to the judgments.

Value

An object of class psi that consists of the following components:

prob

a matrix of discrimination probabilities per stimulus combination.

ntrials

a matrix of number of trials per stimulus combination.

freq

a matrix of frequencies of different answers per stimulus combination.

x, y

(if possible numeric) vectors of stimulus intensities.

See Also

qdm.

Examples

1
2
data(FMrate)
psi1 <- psi(FMrate[FMrate$id == "subj1",])


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