data <- read.table("MACS-cd4-vload0.data.txt")

keep <- !is.na(data[,1]) & !is.na(data[,2]) & !is.na(data[,3]) & 
	!is.na(data[,4]) & !is.na(data[,5]) & !is.na(data[,6]) 
subset <- data.frame( id <- data[keep,1], 
			month <- data[keep,2],
			age <- data[keep,3],
			cd4 <- data[keep,4],
			cd8 <- data[keep,5],
			viral <- data[keep,6] )