NCA: Necessary Condition Analysis
Performs a Necessary Condition Analysis (NCA). (Dul, J. 2016. Necessary Condition Analysis (NCA). ”Logic and Methodology of 'Necessary but not Sufficient' causality." Organizational Research Methods 19(1), 10-52) <doi:10.1177/1094428115584005>.
  NCA identifies necessary (but not sufficient) conditions in datasets, where x causes (e.g. precedes) y. Instead of drawing a regression line ”through the middle of the data” in an xy-plot, NCA draws the ceiling line. The ceiling line y = f(x) separates the area with observations from the area without observations.
  (Nearly) all observations are below the ceiling line: y <= f(x). The empty zone is in the upper left hand corner of the xy-plot (with the convention that the x-axis is ”horizontal” and the y-axis is ”vertical” and that values increase ”upwards” and ”to the right”). The ceiling line is a (piecewise) linear non-decreasing line: a linear step function or a straight line. It indicates which level of x (e.g. an effort or input) is necessary but not sufficient for a (desired) level of y (e.g. good performance or output). A quick start guide for using this package can be found here: <https://repub.eur.nl/pub/78323/> or <https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2624981>.
| Version: | 4.0.3 | 
| Depends: | R (≥ 3.5.0) | 
| Imports: | gplots, quantreg, KernSmooth, lpSolve, ggplot2, doParallel, foreach, iterators, plotly, truncnorm | 
| Suggests: | testthat | 
| Published: | 2025-10-14 | 
| DOI: | 10.32614/CRAN.package.NCA | 
| Author: | Jan Dul [aut],
  Govert Buijs [cre] | 
| Maintainer: | Govert Buijs  <buijs at rsm.nl> | 
| License: | GPL (≥ 3) | 
| URL: | https://www.eur.nl/en/erim/erim/research-initiatives/necessary-condition-analysis | 
| NeedsCompilation: | no | 
| Materials: | NEWS | 
| CRAN checks: | NCA results | 
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