---
title: "introduction_installation"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{introduction_installation}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

# quickpsy

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quickpsy is an R package developed by [Daniel Linares](http://www.dlinares.org) and [Joan López-Moliner](http://www.ub.edu/viscagroup/joan/) to quickly fit and plot psychometric functions for multiple conditions. 

You can find more information at the [website](http://www.dlinares.org/quickpsy.html).


## Installation

You can install the released version of quickpsy from [CRAN](https://CRAN.R-project.org) with:

``` r
install.packages("quickpsy")
```

And the development version from [GitHub](https://github.com/) with:

``` r
# 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

```{r example, fig.height=2, fig.width=6, results='hide'}
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.](https://journal.r-project.org/archive/2016/RJ-2016-008/index.html) The R Journal, 2016, vol. 8, num. 1, p. 122-131.

## Other R packages to fit psychometric functions

* [psyphy](http://cran.r-project.org/web/packages/psyphy/index.html): among other things, it provides links functions to [fit psychometric functions using an approach based on  generalized linear models](http://www.dlinares.org/psychopract.html#fitting-using-generalized-linear-models). 

* [modelfree](http://personalpages.manchester.ac.uk/staff/d.h.foster/software-modelfree/latest/home): fits psychometric functions using a non-parametric approach.