# erf: Utility fnc to compute the components for an empirical... In fungible: Psychometric Functions from the Waller Lab

## Description

Utility function to compute empirical response functions.

## Usage

 `1` ```erf(theta, data, whichItem, min = -3, max = 3, Ncuts = 12) ```

## Arguments

 `theta` Vector of estimated latent trait scores. `data` A matrix of binary item responses. `whichItem` Data for an erf will be generated for whichItem. `min` Default = -3. Minimum value of theta. `max` Default = 3. Maximum value of theta. `Ncuts` Number of score groups for erf.

## Value

 `probs` A vector (of length Ncuts) of bin response probabilities for the empirical response function. `centers` A vector of bin centers. `Ni` Bin sample sizes. `se.p` Standard errors of the estimated bin response probabilities.

Niels Waller

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40``` ```NSubj <- 2000 #generate sample k=1 FMP data b <- matrix(c( #b0 b1 b2 b3 b4 b5 b6 b7 k 1.675, 1.974, -0.068, 0.053, 0, 0, 0, 0, 1, 1.550, 1.805, -0.230, 0.032, 0, 0, 0, 0, 1, 1.282, 1.063, -0.103, 0.003, 0, 0, 0, 0, 1, 0.704, 1.376, -0.107, 0.040, 0, 0, 0, 0, 1, 1.417, 1.413, 0.021, 0.000, 0, 0, 0, 0, 1, -0.008, 1.349, -0.195, 0.144, 0, 0, 0, 0, 1, 0.512, 1.538, -0.089, 0.082, 0, 0, 0, 0, 1, 0.122, 0.601, -0.082, 0.119, 0, 0, 0, 0, 1, 1.801, 1.211, 0.015, 0.000, 0, 0, 0, 0, 1, -0.207, 1.191, 0.066, 0.033, 0, 0, 0, 0, 1, -0.215, 1.291, -0.087, 0.029, 0, 0, 0, 0, 1, 0.259, 0.875, 0.177, 0.072, 0, 0, 0, 0, 1, -0.423, 0.942, 0.064, 0.094, 0, 0, 0, 0, 1, 0.113, 0.795, 0.124, 0.110, 0, 0, 0, 0, 1, 1.030, 1.525, 0.200, 0.076, 0, 0, 0, 0, 1, 0.140, 1.209, 0.082, 0.148, 0, 0, 0, 0, 1, 0.429, 1.480, -0.008, 0.061, 0, 0, 0, 0, 1, 0.089, 0.785, -0.065, 0.018, 0, 0, 0, 0, 1, -0.516, 1.013, 0.016, 0.023, 0, 0, 0, 0, 1, 0.143, 1.315, -0.011, 0.136, 0, 0, 0, 0, 1, 0.347, 0.733, -0.121, 0.041, 0, 0, 0, 0, 1, -0.074, 0.869, 0.013, 0.026, 0, 0, 0, 0, 1, 0.630, 1.484, -0.001, 0.000, 0, 0, 0, 0, 1), nrow=23, ncol=9, byrow=TRUE) theta <- rnorm(NSubj) data<-genFMPData(NSubj = NSubj, bParam = b, theta = theta, seed = 345)\$data erfItem1 <- erf(theta, data, whichItem = 1, min = -3, max = 3, Ncuts = 12) plot( erfItem1\$centers, erfItem1\$probs, type="b", main="Empirical Response Function", xlab = expression(theta), ylab="Probability", cex.lab=1.5) ```

fungible documentation built on Sept. 29, 2021, 1:06 a.m.