Assume I've a (used defined covariance) matrix and I want define the column names like this:
y <- matrix(rnorm(15*10),ncol=15)
colnames(y) <- c("Var1", "Cov12", "Cov13","Cov14", "Cov15",
"Var2", "Cov23", "Cov24", "Cov25",
"Var3", "Cov34" , "Cov35"
"Var4", "Cov45",
"Var5")
where each row contained the variance or co variance for an date t. I want to find a more general way to assign the column names as above, because I'll not always have 5 different variances. I tried something with rep and seq but I didn't find a solution.
Maybe not the most optimal way but we can do
n <- 5
paste0("Var", rep(1:n, n:1), unlist(sapply(2:n, function(x) c("",seq(x, n)))))
[1] "Var1" "Var12" "Var13" "Var14" "Var15" "Var2" "Var23" "Var24" "Var25" "Var3"
"Var34" "Var35" "Var4" "Var45" "Var5"
Breaking it down for better understanding
rep(1:n, n:1)
#[1] 1 1 1 1 1 2 2 2 2 3 3 3 4 4 5
unlist(sapply(2:n, function(x) c("",seq(x, n))))
#[1] "" "2" "3" "4" "5" "" "3" "4" "5" "" "4" "5" "" "5"
We take these outputs and paste them parallely with "Var" to get the desired column names.