fill_NAs = function(file)
{
	dat_with_date = read.csv(file)
	dat = dat_with_date[,-1] #get rid of date column

	line = 1
	n = nrow(dat)
	p = ncol(dat)
	last_noNA_indices = rep(0, p)
	while (line <= n)
	{
		for (i in 1:p)
		{
			if (!is.na(dat[line,i]))
			{
				if (last_noNA_indices[i] < line-1)
				{
					#do some completion
					meanVal = ifelse( last_noNA_indices[i]>0,
						0.5*(dat[last_noNA_indices[i],i]+dat[line,i]),
						dat[line,i] )
					dat[(last_noNA_indices[i]+1):(line-1),i] = meanVal
				}
				last_noNA_indices[i] = line
			}
		}
		line = line + 1
	}

	#complete until end if needed
	for (i in 1:p)
	{
		if (last_noNA_indices[i] < n)
			dat[(last_noNA_indices[i]+1):n,i] = dat[last_noNA_indices[i],i]
	}

	dat_with_date[,2:(p+1)] = dat
	write.csv(dat_with_date, "NONA.csv", row.names=FALSE)
}