Classifier_Bayes function

Classifier based on Bayes rule

A classifier based on Bayes rule, that is maximum a posterior probabilities of class membership

Classifier_Bayes(dat, n, p, g, pi, mu, sigma, ncov = 2)

Arguments

• dat: An $n\times p$ matrix where each row represents an individual observation
• n: Number of observations.
• p: Dimension of observation vecor.
• g: Number of classes.
• pi: A g-dimensional vector for the initial values of the mixing proportions.
• mu: A $p \times g$ matrix for the initial values of the location parameters.
• sigma: A $p\times p$ covariance matrix if ncov=1, or a list of g covariance matrices with dimension $p\times p \times g$ if ncov=2.
• ncov: Options of structure of sigma matrix; the default value is 2; ncov = 1 for a common covariance matrix; ncov = 2 for the unequal covariance/scale matrices.

Returns

• cluster: A vector of the class membership.

Details

The posterior probability can be expressed as

where $\phi$ is a normal probability function with mean $\mu_i$ and covariance matrix $\Sigma_i$, and $z_{ij}$ is is a zero-one indicator variable denoting the class of origin. The Bayes' Classifier of allocation assigns an entity with feature vector $y_j$ to Class $C_k$ if

Examples

n<-150
pi<-c(0.25,0.25,0.25,0.25)
sigma<-array(0,dim=c(3,3,4))
sigma[,,1]<-diag(1,3)
sigma[,,2]<-diag(2,3)
sigma[,,3]<-diag(3,3)
sigma[,,4]<-diag(4,3)
mu<-matrix(c(0.2,0.3,0.4,0.2,0.7,0.6,0.1,0.7,1.6,0.2,1.7,0.6),3,4)
dat<-rmix(n=n,pi=pi,mu=mu,sigma=sigma,ncov=2)
cluster<-Classifier_Bayes(dat=dat$Y,n=150,p=3,g=4,mu=mu,sigma=sigma,pi=pi,ncov=2)