nCng  R Documentation 
This function computes the CNG indices for the eigenvalues of a correlation/covariance matrix (Gorsuch and Nelson, 1981; Nasser, 2002, p. 400; Zoski and Jurs, 1993, p. 6).
nCng(x, cor = TRUE, model = "components", details = TRUE, ...)
x 
numeric: a 
cor 
logical: if 
model 
character: 
details 
logical: if 
... 
variable: additionnal parameters to give to the

Note that the nCng
function is only valid when more than six
eigenvalues are used and that these are obtained in the context of a
principal component analysis. For a factor analysis, some eigenvalues could
be negative and the function will stop and give an error message.
The slope of all possible sets of three adjacent eigenvalues are compared, so CNG indices can be applied only when more than six eigenvalues are used. The eigenvalue at which the greatest difference between two successive slopes occurs is the indicator of the number of components/factors to retain.
nFactors 
numeric: number of factors retained by the CNG procedure. 
details 
numeric: matrix of the details for each index. 
Gilles Raiche
Centre sur les Applications des Modeles de
Reponses aux Items (CAMRI)
Universite du Quebec a Montreal
raiche.gilles@uqam.ca
Gorsuch, R. L. and Nelson, J. (1981). CNG scree test: an objective procedure for determining the number of factors. Presented at the annual meeting of the Society for multivariate experimental psychology.
Nasser, F. (2002). The performance of regressionbased variations of the visual scree for determining the number of common factors. Educational and Psychological Measurement, 62(3), 397419.
Zoski, K. and Jurs, S. (1993). Using multiple regression to determine the number of factors to retain in factor analysis. Multiple Linear Regression Viewpoints, 20(1), 59.
plotuScree
, nScree
,
plotnScree
, plotParallel
## SIMPLE EXAMPLE OF A CNG ANALYSIS data(dFactors) eig < dFactors$Raiche$eigenvalues results < nCng(eig, details=TRUE) results plotuScree(eig, main=paste(results$nFactors, " factors retained by the CNG procedure", sep=""))
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.