binmat2 <- function(len, nbin) {
# Function to make matrix for binning by matrix multiplication
#  len is the length of the input vector
#  nbin is the number by which to bin
# This version puts out vector of same length with repeated elements,
#   makes means for end that doesn't fit within binning
# To bin, multipy binmat2 %*% input
#
# AH 1/2008 

# Set number of unique rows and weighting for mean
n <- len%/%nbin
w <- 1./nbin

# Make empty binning matrix
X <- matrix(0, nrow=len, ncol=len)  

# Fill nonzero elements into matrix
for (i in 1:n){
  colindex <- (i-1)*nbin
  bindex <- colindex+1
  eindex <- colindex + nbin
  for (j in 1:nbin){
    X[colindex+j, bindex:eindex] <- w
  }
}

# Deal with incomplete bins at end, if needed
nend <- len%%nbin
if (nend!=0) {
  w <- 1./nend
  tmp <- len-nend+1
  for (i in tmp:len) {
     X[i, tmp:len] <- w
  }
}

return(X)
}