#' necessary.packages
#' checks if a particular package is installed if not then it installs and loads.
#' @param pkg vector containing names of the packegs required to be loaded
#' @export

necessary.packages<-function(pkg){
  for( i in 1:length(pkg)){
    if((pkg[i] %in% rownames(installed.packages()))){ 
      print(paste("Package ", pkg[i], " is already installed")) 
    }
    if(!(pkg[i] %in% rownames(installed.packages()))){ 
      print(paste("Need to install the package", pkg[i]))
      install.packages(pkg[i])
    }
    
  }
}
necessary.packages(c("MASS", "Matrix", "pscl","distr","rstiefel"))
library(MASS)
library(Matrix)
library(pscl)
library(distr)
library(rstiefel)