How can I insert dimensions of a data matrix into a line of code?

Question

I have a very simple line of code I would like to run. I am creating this vector:

 x1<- rep("T", 576)

However, I derived the number 576 from this line of code:

 dim(x)

(x is a dataframe which is 576 rows long)

I need to create vectors similar to x1 for many other other data frames which are all of varying dimensions. I do not want to have to manually type the dimension value into the rep formula every time. Is there a way to combine these two formulas into one?

Answer 1

Try dim(x)[1] or nrow(x) to extract the dimension and feed into your call:

x1 <- rep("T", nrow(x1))