identifier_columns: Find columns that have a single value across all rows

Description

Identifies columns that have a single value across all rows and returns them.

Usage

identifier_columns(x)
  # S3 method for data.frame
identifier_columns(x)
  # S3 method for exdf
identifier_columns(x)

Value

The return value will be a subset of x, restricted to only include columns whose values are constant. Only one row will be returned.

Arguments

x: A table-like R object such as a data frame or an exdf.

Details

identifier_columns is generic, with methods defined for data frames and exdf objects.

identifier_columns gets the names and values of any columns in a table-like object that have a single unique value. If the object represents a set of data from one replicate, then these special columns are taken to be "identifiers" that describe the replicate. This function is often used inside fitting functions that are passed to by.exdf as its FUN input argument. For example, see the code for fit_ball_berry by typing PhotoGEA::fit_ball_berry in the R terminal.

Examples

Run this code

# Create a simple exdf object
simple_exdf <- exdf(
  data.frame(A = c(3, 2, 7, 9), species = c('a', 'a', 'a', 'a'), plot = c(1, 1, 1, 1)),
  data.frame(A = 'm', species = '', plot = ''),
  data.frame(A = 'Cat1', species = '', plot = '')
)

# Find its identifier columns
identifier_columns(simple_exdf)

# Apply the data frame method to the exdf object's main data frame
identifier_columns(simple_exdf$main_data)