Convert a Long Format Data Set into a Wide Format

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Description

Given a data frame or matrix in long format, convert it to wide format based on the levels of two variables in the data frame. This is a simplified version of the R function reshape with the argument direction="wide".

Usage

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  longToWide(x, data.var, row.var, col.var, 
    row.labels = levels(factor(x[, row.var])), 
    col.labels = levels(factor(x[, col.var])), 
    paste.row.name = FALSE, paste.col.name = FALSE, sep = ".", 
    check.names = FALSE, ...)

Arguments

x

data frame or matrix to convert to wide format. Must have at least 3 columns corresponding to the data variable, row variable, and column variable, respectively.

data.var

character string or numeric scalar indicating column variable name in x for data values.

row.var

character string or numeric scalar indicating column variable name in x for defining rows of output. The indicated column in x cannot have missing values.

col.var

character string or numeric scalar indicating column variable name in x for defining columns of output. The indicated column in x cannot have missing values.

row.labels

optional character vector indicating labels to use for rows. The default value is the levels of the variable indicated by row.var when coerced to a factor.

col.labels

optional character vector indicating labels to use for columns. The default value is the levels of the variable indicated by col.var when coerced to a factor.

paste.row.name

logical scalar indicating whether to paste the name of the variable used to define the row names (i.e., the value of row.var) in front of the values defining the row names. The default value is paste.row.name=FALSE.

paste.col.name

logical scalar indicating whether to paste the name of the variable used to define the column names (i.e., the value of col.var) in front of the values defining the column names. The default value is paste.col.name=FALSE.

sep

character string separator used when paste.row.name=TRUE and/or
paste.col.name=TRUE. The default value is sep=".".

check.names

argument to data.frame. Used to convert the return value to a data frame when the argument x is a data frame. This argument is ignored if x is a matrix.

...

other arguments to data.frame. This argument is ignored if x is a matrix.

Details

The combination of values in x[, row.var] and x[, col.var] must yield n unique values, where n is the number of rows in x.

Value

longToWide returns a matrix when x is a matrix and a data frame when x is a data frame. The number of rows is equal to the number of unique values in x[, row.var] and the number of columns is equal to the number of unique values in x[, col.var].

Author(s)

Steven P. Millard (EnvStats@ProbStatInfo.com), based on a template from Phil Dixon.

See Also

reshape, data.frame, matrix.

Examples

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  EPA.09.Ex.10.1.nickel.df
  #   Month   Well Nickel.ppb
  #1      1 Well.1       58.8
  #2      3 Well.1        1.0
  #3      6 Well.1      262.0
  #4      8 Well.1       56.0
  #5     10 Well.1        8.7
  #6      1 Well.2       19.0
  #7      3 Well.2       81.5
  #8      6 Well.2      331.0
  #9      8 Well.2       14.0
  #10    10 Well.2       64.4
  #11     1 Well.3       39.0
  #12     3 Well.3      151.0
  #13     6 Well.3       27.0
  #14     8 Well.3       21.4
  #15    10 Well.3      578.0
  #16     1 Well.4        3.1
  #17     3 Well.4      942.0
  #18     6 Well.4       85.6
  #19     8 Well.4       10.0
  #20    10 Well.4      637.0

  longToWide(EPA.09.Ex.10.1.nickel.df, 
    "Nickel.ppb", "Month", "Well", paste.row.name = TRUE)
  #         Well.1 Well.2 Well.3 Well.4
  #Month.1    58.8   19.0   39.0    3.1
  #Month.3     1.0   81.5  151.0  942.0
  #Month.6   262.0  331.0   27.0   85.6
  #Month.8    56.0   14.0   21.4   10.0
  #Month.10    8.7   64.4  578.0  637.0

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