# This function looks for a lambda between 0 and 1 such that fbar + lambda*(fq-fbar) has a larger likelihood than that
#of fbar in order to ensure the monotonicity of the algorithm.
#Cbar is the vector weights of fbar (outside the quadratic approximation).
# Cq is the vector weights of fq the minimizer of the quadratic approximation of -loglikelihood.
#likbar is -loglikelihood of fbar.
# we need to make some arrangements in order to be able use the function "LoglikFunc" as it is coded.


Armijo <- function(Cq,Cbar,valfbar,valfq,likbar,K=K,X=X){
lambda <- 1
sumfq <- sum(Cq)
sumfbar <- sum(Cbar)
likq <- LoglikFunc(valfq,Cq)
likfnew <- likq
#if(likfnew == likbar)
#lambda <- 1
count <- 0
while( likfnew >= likbar & count <= 2000){
count <- count +1
lambda <- lambda/2
valfnew <- valfbar + lambda *(valfq - valfbar)
Cfnew  <- Cbar + lambda *(Cq - Cbar)
likfnew <- LoglikFunc(valfnew,Cfnew)
}

lambda
}