Foreach: Loop over Variables in a Data Frame or Environment

In memisc: Tools for Management of Survey Data and the Presentation of Analysis Results

Description

foreach evaluates an expression given as second argument by substituting in variables. The expression may also contain assignments, which take effect in the callers environment.

Usage

  foreach(...)

Arguments

...	tagged and untagged arguments. The tagged arguments define the 'variables' that are looped over, the first untagged argument defines the expression wich is evaluated.

Examples

x <- 1:3
y <- -(1:3)
z <- c("Uri","Schwyz","Unterwalden")
print(x)
print(y)
print(z)
foreach(var=c(x,y,z),          # assigns names
  names(var) <- letters[1:3]   # to the elements of x, y, and z
  )
print(x)
print(y)
print(z)

ds <- data.set(
        a = c(1,2,3,2,3,8,9),
        b = c(2,8,3,2,1,8,9),
        c = c(1,3,2,1,2,8,8)
      )
print(ds)
ds <- within(ds,{ 
      description(a) <- "First item in questionnaire"
      description(b) <- "Second item in questionnaire"
      description(c) <- "Third item in questionnaire"
      
      wording(a) <- "What number do you like first?"
      wording(b) <- "What number do you like second?"
      wording(c) <- "What number do you like third?"

      foreach(x=c(a,b,c),{ # Lazy data documentation:
        labels(x) <- c(    # a,b,c get value labels in one statement
                         one = 1,
                         two = 2,
                       three = 3,
                "don't know" = 8,
         "refused to answer" = 9)
        missing.values(x) <- c(8,9)
        })
      })
      
as.data.frame(ds)

ds <- within(ds,foreach(x=c(a,b,c),{
  measurement(x) <- "interval"
  }))

as.data.frame(ds)

Example output

Loading required package: lattice
Loading required package: MASS

Attaching package: ‘memisc’

The following objects are masked from ‘package:stats’:

    contr.sum, contr.treatment, contrasts

The following object is masked from ‘package:base’:

    as.array

[1] 1 2 3
[1] -1 -2 -3
[1] "Uri"         "Schwyz"      "Unterwalden"
a b c 
1 2 3 
 a  b  c 
-1 -2 -3 
            a             b             c 
        "Uri"      "Schwyz" "Unterwalden" 
  a b c
1 1 2 1
2 2 8 3
3 3 3 2
4 2 2 1
5 3 1 2
6 8 8 8
7 9 9 8
   a  b  c
1  1  2  1
2  2 NA  3
3  3  3  2
4  2  2  1
5  3  1  2
6 NA NA NA
7 NA NA NA
   a  b  c
1  1  2  1
2  2 NA  3
3  3  3  2
4  2  2  1
5  3  1  2
6 NA NA NA
7 NA NA NA

memisc documentation built on May 2, 2019, 5:45 p.m.