CODEWITHSUNDEEP
r
john
john

Reputation: 1036

Renaming Variables Dynamically

I have a file named 'schema'. Based on the file, I need to rename other data frames. For example, 'Var1' of TableA needs to be renamed to 'Col1'. Similarly, VarA of TableA needs to be renamed to ColA. In short, all variables listed in 'FROM' colume of schema needs to be renamed to column 'To'.

Schema <- read.table(header = TRUE, text = 
                  'Tables   From    To
                A   Var1    Col1
                A   Var2    Col2
                A   Var3    Col3
                B   VarA    ColA
                B   VarB    ColB
                B   VarC    ColC
                ')


A <- data.frame(Var1 = 1:3,
                  Var2 = 2:4,
                  Var3 = 3:5)

B <- data.frame(VarA = 1:3,
                VarB = 2:4,
                VarC = 3:5)

Upvotes: 2

Views: 116

Answers (3)

zx8754
zx8754

Reputation: 56149

We could use match:

lapply(list(A = A, B = B), function(i){
  setNames(i, Schema$To[ match(names(i), Schema$From) ])
 })

# $A
#   Col1 Col2 Col3
# 1    1    2    3
# 2    2    3    4
# 3    3    4    5
# 
# $B
#   ColA ColB ColC
# 1    1    2    3
# 2    2    3    4
# 3    3    4    5

Or:

Anew <- setNames(A, Schema$To[ match(names(A), Schema$From) ])
Bnew <- setNames(B, Schema$To[ match(names(B), Schema$From) ])

Or list2env:

list2env(lapply(list(A = A, B = B), function(i){
  setNames(i, Schema$To[ match(names(i), Schema$From) ])
  }), envir = globalenv())

Edit: When there is no match Schema then use keep column name as is:

list2env(lapply(list(A = A, B = B), function(i){
  # check if there is a match, if not keep name unchaged
  x <- as.character(Schema$To[ match(names(i), Schema$From) ])
  ix <- which(is.na(x))
  x[ ix ] <- names(i)[ ix ]
  # retunr with updated names
  setNames(i, x)
  }), envir = globalenv())

Upvotes: 2

ThomasIsCoding
ThomasIsCoding

Reputation: 101343

  • The following code can extract retrieve the name of tables (A and B) from Schema and to the name replacement task:
r <- Map(function(v) function(v) {
  r <- get(v)
  names(r)[names(r) %in% Schema$From] <- as.character(Schema$To[Schema$From %in% names(r)])
  assign(v,r)},
    as.character(unique(Schema$Tables)))

which gives

> r
$A
  Col1 Col2 Col3
1    1    2    3
2    2    3    4
3    3    4    5

$B
  ColA ColB ColC
1    1    2    3
2    2    3    4
3    3    4    5
  • If you don't want result as list, you can do something like
list2env(Map(function(v) {
  r <- get(v)
  names(r)[names(r) %in% Schema$From] <- as.character(Schema$To[Schema$From %in% names(r)])
  assign(v,r)},
  as.character(unique(Schema$Tables))),envir = .GlobalEnv)

or

for (v in as.character(unique(Schema$Tables))) {
  r <- get(v)
  names(r)[names(r) %in% Schema$From] <- as.character(Schema$To[Schema$From %in% names(r)])
  assign(v,r)
}

then you will keep your object A and B

> A
  Col1 Col2 Col3
1    1    2    3
2    2    3    4
3    3    4    5
> B
  ColA ColB ColC
1    1    2    3
2    2    3    4
3    3    4    5

Upvotes: 1

s_baldur
s_baldur

Reputation: 33488

lut <- setNames(as.character(Schema$To), Schema$From)

setNames(A, lut[names(A)])

  Col1 Col2 Col3
1    1    2    3
2    2    3    4
3    3    4    5

setNames(B, lut[names(B)])

  ColA ColB ColC
1    1    2    3
2    2    3    4
3    3    4    5

Upvotes: 1

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