Extended data frame — exdf • PhotoGEA

An "extended data frame" (exdf) is an object similar to a data frame, but which also contains information about the units and categories of each column.

Usage

exdf(
    main_data = data.frame(),
    units = NULL,
    categories = NULL,
    ...
  )

Arguments

main_data: A data frame.
units: A data frame with the same columns as main_data (or a subset of the columns in main_data) but with just one row, where each entry describes the units for the corresponding column of main_data. If units is NULL, it will be initialized with NA for each column. The units of any columns in main_data that are not present in units will also be initialized to NA.
categories: A data frame with the same columns as main_data (or a subset of the columns in main_data) but with just one row, where each entry describes the category for the corresponding column of main_data. If categories is NULL, it will be initialized with NA for each column. The categories of any columns in main_data that are not present in catgories will also be initialized to NA.
...: Any additional properties to include as entries in the resulting exdf object; these must be passed as named arguments.

Details

The exdf class was originally created as a way to represent the contents of a Licor Excel file in an R structure. In Licor Excel files, each column has a name, units, and a category; for example, the column for values of net assimilation rate is called A, has units of micromol / m^2 / s, and is categorized as a GasEx variable.

From a technical point of view, an exdf object is simply a list with three required elements: main_data, units, and categories. Each of these should be a data frame with the same column names, as described above. It is also possible for an exdf object to have additional entries such as a filename that stores the name of the file that was used to create the exdf.

Several S3 methods have been defined for exdf objects, following the general guidance from Advanced R on S3 classes:

Note that the column names of main_data, units, and categories must be unique; the make.unique function can be useful for ensuring this.

Value

An exdf object as described above.

Examples

# Example 1: Creating a simple exdf object with two columns (`A` and `B`) and
# default values for its units and categories. There are four values of each
# variable.
exdf(data.frame(A = c(3, 2, 7, 9), B = c(4, 5, 1, 8)))
#> 
#> Converting an `exdf` object to a `data.frame` before printing
#> 
#>   A [NA] (NA) B [NA] (NA)
#> 1           3           4
#> 2           2           5
#> 3           7           1
#> 4           9           8

# Example 2: Creating a simple exdf object with two columns (`A` and `B`) that
# have units of `m` and `s`, respectively, and categories of `Cat1` and `Cat2`,
# respectively. There are four values of each variable.
exdf(
  data.frame(A = c(3, 2, 7, 9), B = c(4, 5, 1, 8)),
  data.frame(A = 'm', B = 's'),
  data.frame(A = 'Cat1', B = 'Cat2')
)
#> 
#> Converting an `exdf` object to a `data.frame` before printing
#> 
#>   A [Cat1] (m) B [Cat2] (s)
#> 1            3            4
#> 2            2            5
#> 3            7            1
#> 4            9            8