Looping across time series values in R

I apologize if I have overlooked a solution to this somewhere, but I have spent what seems like an unjustifiable amount of time trying to get a solution to this. I want to manipulate multiple time series values and a solution to the simple task below may help:

x1 <- c(1, 11, 21)
y1 <- c(2, 12, 22)
x2 <- c(3, 13, 23)
y2 <- c(4, 14, 24)
x3 <- c(5, 15, 25)
y4 <- c(6, 16, 26)

Assume the above values go up to x60 and y60.

z1 <- x1 + y1
z2 <- x2 + y2 
z3 <- x3 + y3

I need to generate the values z1, z2… with loops. Something along the lines of:

for (i in 1:3){
  obj1= paste0("x",i)
  obj2= paste0("y", i)
  dv<- paste0("z", i)
  assign(dv, obj1 + obj2)
}

(ofcourse this doesn’t run). Any ideas?

>Solution :

We can use mget to retrieve the ‘x’ object values into a list and likewise the y object values, then loop over the corresponding list with Map and add them (+) and return a list. If we need to create ‘z’ objects in the global env (not recommended), set the names of the output list with ‘z1’, ‘z2’, etc and then use list2env

lst1 <- Map(`+`, mget(ls(pattern = "^x\\d+$")),
                 mget(ls(pattern = "^y\\d+$")))
names(lst1) <- paste0("z", seq_along(lst1))
list2env(lst1, .GlobalEnv)

The for loop didn’t run because the operator (+) is applied on the object name strings and not the value. We can use get here

for (i in 1:3){
  obj1= paste0("x",i)
  obj2= paste0("y", i)
  dv<- paste0("z", i)
  assign(dv, get(obj1) + get(obj2))
}

For the edited case, we may do

fmla <- paste0(paste0("psr_", 1:60), "~", paste0("unemp_", 1:60))
lapply(fmla, function(fml) td(as.formula(fml), "average"))