Utilities for Data Manipulation

David Gerbing

library("lessR")

Recode Data Values

Data transformations for continuous variables are straightforward, just enter the arithmetic expression for the transformation. For each variable identify the corresponding data frame that contains the variable if there is one. For example, the following creates a new variable xsq that is the square of the values of a variable x in the d data frame.

d$xsq <- d$x^2

Or, use the base R transform() function to accomplish the same, plus other functions from other packages that accomplish the same result.

For variables that define discrete categories, however, the transformation may not be so straightforward with base R functions such as a nested string of ifelse() functions. An alternative is the lessR function recode().

To use recode(), specify the variable to be recoded with the old_vars parameter, the first parameter in the function call. Specify values to be recoded with the required old parameter. Specify the corresponding recoded values with the required new parameter. There must be a 1-to-1 correspondence between the two sets of values, such as 0:5 recoded to 5:0, six items in the old set and six items in the new set.

Examples

To illustrate, construct the following small data frame.

d <- read.table(text="Severity Description
1 Mild
4 Moderate
3 Moderate
2 Mild
1 Severe", header=TRUE, stringsAsFactors=FALSE)

d
##   Severity Description
## 1        1        Mild
## 2        4    Moderate
## 3        3    Moderate
## 4        2        Mild
## 5        1      Severe

Now change the integer values of the variable Severity from 1 through 4 to 10 through 40. Because the parameter old_vars is the first parameter in the definition of recode(), and because it is listed first, the parameter name need not be specified. The default data frame is d, otherwise specify with the data parameter.

d <- recode(Severity, old=1:4, new=c(10,20,30,40))
## 
## --------------------------------------------------------
## First four rows of data to recode for data frame: d 
## --------------------------------------------------------
##   Severity
## 1        1
## 2        4
## 3        3
## 4        2
## 
## 
## Recoding Specification
## ----------------------
##    1 --> 10 
##    2 --> 20 
##    3 --> 30 
##    4 --> 40 
## 
## Number of cases (rows) to recode: 5 
## 
## Replace existing values of each specified variable, no value for option: new.var
## 
## ---  Recode: Severity ---------------------------------
## Number of unique values of Severity in the data: 4 
## Number of values of Severity to recode: 4 
## 
## 
## ------------------------------------------------
## First four rows of recoded data
## ------------------------------------------------
##   Severity
## 1       10
## 2       40
## 3       30
## 4       20
d
##   Severity Description
## 1       10        Mild
## 2       40    Moderate
## 3       30    Moderate
## 4       20        Mild
## 5       10      Severe

In the previous example, the values of the variable were overwritten with the new values. In the following example, instead write the recoded values to a new variable with the new_vars parameter, here SevereNew.

d <- recode(Severity, new_vars="SevereNew", old=1:4, new=c(10,20,30,40))
## 
## --------------------------------------------------------
## First four rows of data to recode for data frame: d 
## --------------------------------------------------------
##   Severity
## 1       10
## 2       40
## 3       30
## 4       20
## 
## 
## Recoding Specification
## ----------------------
##    1 --> 10 
##    2 --> 20 
##    3 --> 30 
##    4 --> 40 
## 
## Number of cases (rows) to recode: 5 
## 
## ---  Recode: Severity ---------------------------------
## Unique values of Severity in the data: 10 20 30 40 
## Number of unique values of Severity in the data: 4 
## >>> Note: A value specified to recode, 1, is not in the data.
## 
## >>> Note: A value specified to recode, 2, is not in the data.
## 
## >>> Note: A value specified to recode, 3, is not in the data.
## 
## >>> Note: A value specified to recode, 4, is not in the data.
## 
## Number of values of Severity to recode: 4 
## Recode to variable: SevereNew 
## 
## 
## ------------------------------------------------
## First four rows of recoded data
## ------------------------------------------------
##   Severity SevereNew
## 1       10        10
## 2       40        40
## 3       30        30
## 4       20        20

A convenient application of recode() is to Likert data, with responses scored to items on a survey such as from 0 for Strongly Disagree to 5 for Strongly Agree. To encourage responders to carefully read the items, some items are written in the opposite direction so that disagreement indicates agreement with the overall attitude being assessed.

As an example, reverse score Items m01, m02, m03, and m10 from survey responses to the 20-item Mach IV scale. That is, score a 0 as a 5 and so forth. The responses are included as part of lessR and so can be directly read.

d <- Read("Mach4")
## 
## >>> Suggestions
## Details about your data, Enter:  details()  for d, or  details(name)
## 
## Data Types
## ------------------------------------------------------------
## integer: Numeric data values, integers only
## ------------------------------------------------------------
## 
##     Variable                  Missing  Unique 
##         Name     Type  Values  Values  Values   First and last values
## ------------------------------------------------------------------------------------------
##  1    Gender   integer    351       0       2   0  0  1 ... 0  0  1
##  2       m01   integer    351       0       6   0  0  2 ... 2  1  3
##  3       m02   integer    351       0       6   4  1  1 ... 3  4  3
##  4       m03   integer    351       0       6   1  4  0 ... 3  4  3
##  5       m04   integer    351       0       6   5  4  5 ... 3  4  4
##  6       m05   integer    351       0       6   0  0  4 ... 2  3  3
##  7       m06   integer    351       0       6   5  3  4 ... 4  4  2
##  8       m07   integer    351       0       6   4  3  0 ... 4  4  2
##  9       m08   integer    351       0       6   1  0  5 ... 3  2  3
## 10       m09   integer    351       0       6   5  4  3 ... 3  3  3
## 11       m10   integer    351       0       6   4  4  4 ... 3  4  3
## 12       m11   integer    351       0       6   0  0  1 ... 1  1  2
## 13       m12   integer    351       0       6   0  1  4 ... 2  1  3
## 14       m13   integer    351       0       6   0  1  0 ... 3  1  2
## 15       m14   integer    351       0       6   0  1  0 ... 2  2  2
## 16       m15   integer    351       0       6   4  2  2 ... 3  5  3
## 17       m16   integer    351       0       6   0  4  0 ... 0  2  5
## 18       m17   integer    351       0       6   1  4  2 ... 0  2  2
## 19       m18   integer    351       0       6   3  3  4 ... 4  4  3
## 20       m19   integer    351       0       6   2  1  0 ... 0  0  1
## 21       m20   integer    351       0       6   4  0  1 ... 1  0  3
## ------------------------------------------------------------------------------------------
d <- recode(c(m01:m03,m10), old=0:5, new=5:0)
## 
## --------------------------------------------------------
## First four rows of data to recode for data frame: d 
## --------------------------------------------------------
##   m01 m02 m03 m10
## 1   0   4   1   4
## 2   0   1   4   4
## 3   2   1   0   4
## 4   0   5   2   2
## 
## 
## Recoding Specification
## ----------------------
##    0 --> 5 
##    1 --> 4 
##    2 --> 3 
##    3 --> 2 
##    4 --> 1 
##    5 --> 0 
## 
## Number of cases (rows) to recode: 351 
## 
## Replace existing values of each specified variable, no value for option: new.var
## 
## ---  Recode: m01 ---------------------------------
## Number of unique values of m01 in the data: 6 
## Number of values of m01 to recode: 6 
## 
## ---  Recode: m02 ---------------------------------
## Number of unique values of m02 in the data: 6 
## Number of values of m02 to recode: 6 
## 
## ---  Recode: m03 ---------------------------------
## Number of unique values of m03 in the data: 6 
## Number of values of m03 to recode: 6 
## 
## ---  Recode: m10 ---------------------------------
## Number of unique values of m10 in the data: 6 
## Number of values of m10 to recode: 6 
## 
## 
## ------------------------------------------------
## First four rows of recoded data
## ------------------------------------------------
##   m01 m02 m03 m10
## 1   5   1   4   1
## 2   5   4   1   1
## 3   3   4   5   1
## 4   5   0   3   3

Missing Data

The function also addresses missing data. Existing data values can be converted to an R missing value. In this example, all values of 1 for the variable Plan are considered missing.

d <- Read("Employee")
## 
## >>> Suggestions
## Details about your data, Enter:  details()  for d, or  details(name)
## 
## Data Types
## ------------------------------------------------------------
## character: Non-numeric data values
## integer: Numeric data values, integers only
## double: Numeric data values with decimal digits
## ------------------------------------------------------------
## 
##     Variable                  Missing  Unique 
##         Name     Type  Values  Values  Values   First and last values
## ------------------------------------------------------------------------------------------
##  1     Years   integer     36       1      16   7  NA  15 ... 1  2  10
##  2    Gender character     37       0       2   M  M  M ... F  F  M
##  3      Dept character     36       1       5   ADMN  SALE  SALE ... MKTG  SALE  FINC
##  4    Salary    double     37       0      37   53788.26  94494.58 ... 56508.32  57562.36
##  5    JobSat character     35       2       3   med  low  low ... high  low  high
##  6      Plan   integer     37       0       3   1  1  3 ... 2  2  1
##  7       Pre   integer     37       0      27   82  62  96 ... 83  59  80
##  8      Post   integer     37       0      22   92  74  97 ... 90  71  87
## ------------------------------------------------------------------------------------------
newdata <- recode(Plan, old=1, new="missing")
## 
## --------------------------------------------------------
## First four rows of data to recode for data frame: d 
## --------------------------------------------------------
##                  Plan
## Ritchie, Darnell    1
## Wu, James           1
## Hoang, Binh         3
## Jones, Alissa       1
## 
## 
## Recoding Specification
## ----------------------
##    1 --> missing 
## 
## 
## R represents missing data with a NA for 'not assigned'.
## 
## Number of cases (rows) to recode: 37 
## 
## Replace existing values of each specified variable, no value for option: new.var
## 
## ---  Recode: Plan ---------------------------------
## Number of unique values of Plan in the data: 3 
## Number of values of Plan to recode: 1 
## 
## 
## ------------------------------------------------
## First four rows of recoded data
## ------------------------------------------------
##                  Plan
## Ritchie, Darnell   NA
## Wu, James          NA
## Hoang, Binh         3
## Jones, Alissa      NA

Now values of 1 for Plan are missing, having the value of NA for not available, as shown by listing the first six rows of data with the base R function head().

head(d)
##                  Years Gender Dept    Salary JobSat Plan Pre Post
## Ritchie, Darnell     7      M ADMN  53788.26    med    1  82   92
## Wu, James           NA      M SALE  94494.58    low    1  62   74
## Hoang, Binh         15      M SALE 111074.86    low    3  96   97
## Jones, Alissa        5      F <NA>  53772.58   <NA>    1  65   62
## Downs, Deborah       7      F FINC  57139.90   high    2  90   86
## Afshari, Anbar       6      F ADMN  69441.93   high    2 100  100

The procedure can be reversed in which values that are missing according to the R code NA are converted to non-missing values. To illustrate with the Employee data set, examine the first six rows of data. The value of Years is missing in the second row of data.

d <- Read("Employee")
## 
## >>> Suggestions
## Details about your data, Enter:  details()  for d, or  details(name)
## 
## Data Types
## ------------------------------------------------------------
## character: Non-numeric data values
## integer: Numeric data values, integers only
## double: Numeric data values with decimal digits
## ------------------------------------------------------------
## 
##     Variable                  Missing  Unique 
##         Name     Type  Values  Values  Values   First and last values
## ------------------------------------------------------------------------------------------
##  1     Years   integer     36       1      16   7  NA  15 ... 1  2  10
##  2    Gender character     37       0       2   M  M  M ... F  F  M
##  3      Dept character     36       1       5   ADMN  SALE  SALE ... MKTG  SALE  FINC
##  4    Salary    double     37       0      37   53788.26  94494.58 ... 56508.32  57562.36
##  5    JobSat character     35       2       3   med  low  low ... high  low  high
##  6      Plan   integer     37       0       3   1  1  3 ... 2  2  1
##  7       Pre   integer     37       0      27   82  62  96 ... 83  59  80
##  8      Post   integer     37       0      22   92  74  97 ... 90  71  87
## ------------------------------------------------------------------------------------------
head(d)
##                  Years Gender Dept    Salary JobSat Plan Pre Post
## Ritchie, Darnell     7      M ADMN  53788.26    med    1  82   92
## Wu, James           NA      M SALE  94494.58    low    1  62   74
## Hoang, Binh         15      M SALE 111074.86    low    3  96   97
## Jones, Alissa        5      F <NA>  53772.58   <NA>    1  65   62
## Downs, Deborah       7      F FINC  57139.90   high    2  90   86
## Afshari, Anbar       6      F ADMN  69441.93   high    2 100  100

Here convert all missing data values for the variables Years and Salary to the value of 99.

d <- recode(c(Years, Salary), old="missing", new=99)
## 
## --------------------------------------------------------
## First four rows of data to recode for data frame: d 
## --------------------------------------------------------
##                  Years    Salary
## Ritchie, Darnell     7  53788.26
## Wu, James           NA  94494.58
## Hoang, Binh         15 111074.86
## Jones, Alissa        5  53772.58
## 
## 
## Recoding Specification
## ----------------------
##    missing --> 99 
## 
## Number of cases (rows) to recode: 37 
## 
## Replace existing values of each specified variable, no value for option: new.var
## 
## ---  Recode: Years ---------------------------------
## Number of unique values of Years in the data: 16 
## >>> Note: A value specified to recode, missing, is not in the data.
## 
## Number of values of Years to recode: 1 
## 
## ---  Recode: Salary ---------------------------------
## Unique values of Salary in the data: 46124.97 49188.96 49704.79 49868.68 51036.85 53772.58 53788.26 55545.25 56508.32 56772.95 57139.9 57562.36 61055.44 61356.69 61961.29 66312.89 66337.83 69441.93 69547.6 69624.87 71084.02 72321.36 72502.5 72675.26 77714.85 81871.05 83014.43 87785.51 91352.33 92681.19 94494.58 95027.55 99062.66 108138.4 111074.9 122563.4 134419.2 
## Number of unique values of Salary in the data: 37 
## >>> Note: A value specified to recode, missing, is not in the data.
## 
## Number of values of Salary to recode: 1 
## 
## 
## ------------------------------------------------
## First four rows of recoded data
## ------------------------------------------------
##                  Years    Salary
## Ritchie, Darnell     7  53788.26
## Wu, James           99  94494.58
## Hoang, Binh         15 111074.86
## Jones, Alissa        5  53772.58
head(d)
##                  Years Gender Dept    Salary JobSat Plan Pre Post
## Ritchie, Darnell     7      M ADMN  53788.26    med    1  82   92
## Wu, James           99      M SALE  94494.58    low    1  62   74
## Hoang, Binh         15      M SALE 111074.86    low    3  96   97
## Jones, Alissa        5      F <NA>  53772.58   <NA>    1  65   62
## Downs, Deborah       7      F FINC  57139.90   high    2  90   86
## Afshari, Anbar       6      F ADMN  69441.93   high    2 100  100

Now the value of Years in the second row of data is 99.

Sort Rows of Data

Sorts the values of a data frame according to the values of one or more variables contained in the data frame, or the row names. Variable types include numeric and factor variables. Factors are sorted by the ordering of their values, which, by default is alphabetical. Sorting by row names is also possible.

To illustrate, use the lessR Employee data set, here just the first 12 rows of data to save space.

d <- Read("Employee")
## 
## >>> Suggestions
## Details about your data, Enter:  details()  for d, or  details(name)
## 
## Data Types
## ------------------------------------------------------------
## character: Non-numeric data values
## integer: Numeric data values, integers only
## double: Numeric data values with decimal digits
## ------------------------------------------------------------
## 
##     Variable                  Missing  Unique 
##         Name     Type  Values  Values  Values   First and last values
## ------------------------------------------------------------------------------------------
##  1     Years   integer     36       1      16   7  NA  15 ... 1  2  10
##  2    Gender character     37       0       2   M  M  M ... F  F  M
##  3      Dept character     36       1       5   ADMN  SALE  SALE ... MKTG  SALE  FINC
##  4    Salary    double     37       0      37   53788.26  94494.58 ... 56508.32  57562.36
##  5    JobSat character     35       2       3   med  low  low ... high  low  high
##  6      Plan   integer     37       0       3   1  1  3 ... 2  2  1
##  7       Pre   integer     37       0      27   82  62  96 ... 83  59  80
##  8      Post   integer     37       0      22   92  74  97 ... 90  71  87
## ------------------------------------------------------------------------------------------
d <- d[1:12,]
d <- Sort(d, Gender)
## 
## Sort Specification
##   2 -->  ascending
d
##                  Years Gender Dept    Salary JobSat Plan Pre Post
## Jones, Alissa        5      F <NA>  53772.58   <NA>    1  65   62
## Downs, Deborah       7      F FINC  57139.90   high    2  90   86
## Afshari, Anbar       6      F ADMN  69441.93   high    2 100  100
## Kimball, Claire      8      F MKTG  61356.69   high    2  93   92
## Cooper, Lindsay      4      F MKTG  56772.95   high    1  78   91
## Saechao, Suzanne     8      F SALE  55545.25    med    1  98  100
## Ritchie, Darnell     7      M ADMN  53788.26    med    1  82   92
## Wu, James           NA      M SALE  94494.58    low    1  62   74
## Hoang, Binh         15      M SALE 111074.86    low    3  96   97
## Knox, Michael       18      M MKTG  99062.66    med    3  81   84
## Campagna, Justin     8      M SALE  72321.36    low    1  76   84
## Pham, Scott         13      M SALE  81871.05   high    2  90   94
d <- Sort(d, c(Gender, Salary), direction=c("+", "-"))
## 
## Sort Specification
##   2 -->  ascending 
##   4 -->  descending
d
##                  Years Gender Dept    Salary JobSat Plan Pre Post
## Afshari, Anbar       6      F ADMN  69441.93   high    2 100  100
## Kimball, Claire      8      F MKTG  61356.69   high    2  93   92
## Downs, Deborah       7      F FINC  57139.90   high    2  90   86
## Cooper, Lindsay      4      F MKTG  56772.95   high    1  78   91
## Saechao, Suzanne     8      F SALE  55545.25    med    1  98  100
## Jones, Alissa        5      F <NA>  53772.58   <NA>    1  65   62
## Hoang, Binh         15      M SALE 111074.86    low    3  96   97
## Knox, Michael       18      M MKTG  99062.66    med    3  81   84
## Wu, James           NA      M SALE  94494.58    low    1  62   74
## Pham, Scott         13      M SALE  81871.05   high    2  90   94
## Campagna, Justin     8      M SALE  72321.36    low    1  76   84
## Ritchie, Darnell     7      M ADMN  53788.26    med    1  82   92

Sort by row names in ascending order.

d <- Sort(d, row.names)
## 
## Sort Specification
##   row.names -->  ascending
d
##                  Years Gender Dept    Salary JobSat Plan Pre Post
## Afshari, Anbar       6      F ADMN  69441.93   high    2 100  100
## Campagna, Justin     8      M SALE  72321.36    low    1  76   84
## Cooper, Lindsay      4      F MKTG  56772.95   high    1  78   91
## Downs, Deborah       7      F FINC  57139.90   high    2  90   86
## Hoang, Binh         15      M SALE 111074.86    low    3  96   97
## Jones, Alissa        5      F <NA>  53772.58   <NA>    1  65   62
## Kimball, Claire      8      F MKTG  61356.69   high    2  93   92
## Knox, Michael       18      M MKTG  99062.66    med    3  81   84
## Pham, Scott         13      M SALE  81871.05   high    2  90   94
## Ritchie, Darnell     7      M ADMN  53788.26    med    1  82   92
## Saechao, Suzanne     8      F SALE  55545.25    med    1  98  100
## Wu, James           NA      M SALE  94494.58    low    1  62   74

Randomize the order of the data values.

d <- Sort(d, random)
## 
## Sort Specification
##   random
d
##                  Years Gender Dept    Salary JobSat Plan Pre Post
## Kimball, Claire      8      F MKTG  61356.69   high    2  93   92
## Downs, Deborah       7      F FINC  57139.90   high    2  90   86
## Saechao, Suzanne     8      F SALE  55545.25    med    1  98  100
## Knox, Michael       18      M MKTG  99062.66    med    3  81   84
## Campagna, Justin     8      M SALE  72321.36    low    1  76   84
## Ritchie, Darnell     7      M ADMN  53788.26    med    1  82   92
## Hoang, Binh         15      M SALE 111074.86    low    3  96   97
## Pham, Scott         13      M SALE  81871.05   high    2  90   94
## Cooper, Lindsay      4      F MKTG  56772.95   high    1  78   91
## Wu, James           NA      M SALE  94494.58    low    1  62   74
## Afshari, Anbar       6      F ADMN  69441.93   high    2 100  100
## Jones, Alissa        5      F <NA>  53772.58   <NA>    1  65   62

Rescale Data

rescale(Salary)
##  [1] -0.545 -0.757 -0.837  1.347  0.005 -0.925  1.950  0.484 -0.775  1.118 -0.139 -0.926

Create Factor Variables

d <- rd("Mach4", quiet=TRUE)
l <- rd("Mach4_lbl")
## 
## >>> Suggestions
## Details about your data, Enter:  details()  for d, or  details(name)
## 
## Data Types
## ------------------------------------------------------------
## character: Non-numeric data values
## ------------------------------------------------------------
## 
##     Variable                  Missing  Unique 
##         Name     Type  Values  Values  Values   First and last values
## ------------------------------------------------------------------------------------------
##  1     label character     20       0      20   Never tell anyone the real reason you did something unless it is useful to do so ... Most people forget more easily the death of a parent than the loss of their property
## ------------------------------------------------------------------------------------------
LikertCats <- c("Strongly Disagree", "Disagree", "Slightly Disagree",
                "Slightly Agree", "Agree", "Strongly Agree")
d <- factors(m01:m20, levels=0:5, labels=LikertCats)

Convert the specified variables to factors according to the given vector of three variables only. Leave the original variables unmodified, create new variables.

d <- factors(c(m06, m07, m20), levels=0:5, labels=LikertCats, new=TRUE)

Now copy the variable labels from the original integer variables to the newly created factor variables.

l <- factors(c(m06, m07, m20), var_labels=TRUE)