quickpsy is an R package developed by Daniel Linares and Joan López-Moliner to quickly fit and plot psychometric functions for multiple conditions.

## Installation

You can install the released version of quickpsy from CRAN with:

install.packages("quickpsy")

And the development version from GitHub with:

# install.packages("devtools")
devtools::install_github("danilinares/quickpsy")

At present, the development version of quickpsy is slower than older versions. If you need to perform bootstrap for many conditions you might want to use an older version.

## Example

library(quickpsy)

fit <- quickpsy(qpdat, phase, resp, grouping = c("participant", "cond"))

plot(fit, color = cond)

## Features

• Fits and plots multiple conditions with minimal coding.

• The user does not need to introduce initial parameters for default shapes of the psychometric functions.

• Calculates parametric and non-parametric bootstrap confidence intervals.

• Compares parameters and thresholds for different conditions using bootstrap.

• Guess and lapses can be fixed or free as parameters.

• Fits cumulative normal, logistic, weibull functions or any function defined by the user.

• Facilitates the reading of several data files.

### Development version (at present it is slower than the CRAN version)

• Different conditions could share parameters.

• Easy model comparisons using likelihood ratios or Akaike information criterion.

## Citation

Linares, D., & López-Moliner, J. (2016). quickpsy: An R package to fit psychometric functions for multiple groups. The R Journal, 2016, vol. 8, num. 1, p. 122-131.