NCA Software

The NCA software is free software that can be used with the free programming language R. 

======VERSION 3.3.1 is available======

In NCA 3.3.0, a few larger changes are implemented and version 3.3.1 a bug in nca_outliers is fixed.

The function nca_outliers is extended in several ways. By specifying the number of potential outliers (kit is now possible to analyse several potential outliers at onceWith the min.dif argument it is possible to specify the minimum effect size difference for identifying a case as a potential outlier. With  max.results it is possible to specify the maximum number of potential outliers to be reported. Furthermore, the arguments cornerflip.x and flip.y that are known from the nca_analysis function are also added. (more information about outliers can be found  on

In the nca_analysis function, the theoretical scope can be specified with the scope argument by specified the values of the theoretical minima and maxima of X and Y, e.g., scope = c(23,54,210,430). The new version allows NA ‘values’, indicating that the empirical minimum or maximum value must be selected. This allows for having a scope with theoretical minimum/maximum values for only X or for only Y, for example scope = c(NA,NA,210,430). For multiple conditions, multiple scopes can be defined using a list, for example. scope = list (c(NA,NA, 210,430), c(100, 300,210,430)).

To align the software with the basic standards of good NCA practice (see the default value for the

plots argument in nca_output function is changed to plots = TRUE, and in the short printed summary of nca_analysis the effect size is expressed with a precision of 2 digits after the decimal point.   

If you have installed an older version of the NCA package you can update the package as follows:


The NCA package uses other packages. It is possible that these packages that are not installed on your computer. In that case the following error message may appear: There is no package called … , where … corresponds to the name of the missing package. You then need to install the specific packages first.


If you install the package for the first time: see the Quick Start Guide. A novice user without knowledge of R or NCA can install the software on the user’s computer and perform an NCA analysis within 15 minutes. 

If you have installed an older version of the NCA package you can update the package as follows:


A Quick Start Guide is available, and also a demonstration of conducting NCA in three steps.

The software draws ceiling lines and produces several NCA parameters (including necessity effect size) to interpret the results.

An example is shown here.

A video explanation of the bottleneck table , and a video demonstration on how to produce the bottleneck table with the NCA software are available.