R: Product of elements of a matrix

prod.index {PhylogeneticEM} | R Documentation

## Product of elements of a matrix

### Description

`prod.index` return the product of chosen elements of a matrix.

### Usage

    ## S3 method for class 'index'
    prod(X, Id)

### Arguments

`X` | a matrix with p rows and K column. Each row contains the number of partition in 1<=k<=K groups for one of the p children of a given node
`Id` | a vector of length p, result of the function `xsimplex`.

### Details

This function is to be used in `sum.simplex` to be applied to all the elements given by `xsimplex`. Performs the product : X[1,Id[1]]*X[2,Id[2]]*...*X[p,Id[p]] if all the elements of Id are positive. Otherwise, just return 0.

### Value

double : the result of the product.

[Package PhylogeneticEM version 1.1.0 Index]