how to create an object from a vector insde a loop?-CodePudding

I'm in the situation where I would like to create an object from a character vector. For example:

v <- c("ind1_2015", "ind1_2016", "ind1_2017")

for (ind in v) {
 ind <- readRDS(paste0(ind, ".RDS"))
}

so at the end I would like to have 3 data frames, each one called ind1_2015, ind1_2016 and ind1_2017. How can I achieve this?

CodePudding user response：

You could use assign:

v <- c("ind1_2015", "ind1_2016", "ind1_2017")

for(ind in v) {
        
        assign(ind, data.frame(v = ind))
}

CodePudding user response：

assign can be used here, in this example resulting in three dataframes called df_ind1_2015, df_ind1_2016, and df_ind1_2017 :

v <- c("ind1_2015", "ind1_2016", "ind1_2017")

for(ind in v) {
  value <- readRDS(paste0(ind, ".RDS"))
  assign(x = paste0("df_", ind), value = value)
}

CodePudding user response：

In R this is different from Python or similar. Initialize a named list but loop over the (numeric) indices.

for (i in seq_along(v)) {
  ind[[i]] <- readRDS(paste0(v[[i]], ".rds"))
}
ind
# $ind1_2015
#   X1 X2 X3 X4
# 1  1  4  7 10
# 2  2  5  8 11
# 3  3  6  9 12
# 
# $ind1_2016
#   X1 X2 X3 X4
# 1  1  4  7 10
# 2  2  5  8 11
# 3  3  6  9 12
# 
# $ind1_2017
#   X1 X2 X3 X4
# 1  1  4  7 10
# 2  2  5  8 11
# 3  3  6  9 12

Alternatively use lapply

ind <- lapply(setNames(v, v), \(x) readRDS(paste0(x, '.rds')))

To "unpack" the list use list2env(ind, .GlobalEnv) to get single data frames (not necessarily recommended).

Data:

ind1_2015 <- ind1_2016 <- ind1_2017 <- data.frame(matrix(1:12, 3, 4))
lapply(c("ind1_2015", "ind1_2016", "ind1_2017"), \(x) saveRDS(get(x), paste0(x, '.rds')))