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Unfold n-dimensional measurement to 1D

Source: R/nd_reduce.R
measure_unfold.Rd

Converts an n-dimensional measurement to a 1D vector by flattening according to a specified dimension order. Stores metadata needed to reconstruct the original nD structure via measure_fold().

Usage

measure_unfold(x, order = NULL)

Arguments

x

A measure_nd_tbl or measure_nd_list object.

order

Integer vector specifying the order of dimensions for unfolding. Default is NULL, which uses the natural order (1, 2, ..., n). The first dimension varies fastest.

Value

A measure_tbl or measure_list with an attribute "fold_info" containing the metadata needed to reconstruct the nD structure.

Details

Unfolding is useful for:

  • Applying 1D modeling techniques (PCA, PLS) to nD data

  • Exporting to formats that expect 1D vectors

  • Visualization as a single trace

The fold metadata includes:

  • ndim: Original number of dimensions

  • dim_names, dim_units: Original dimension metadata

  • coordinates: The original coordinate values for each dimension

  • order: The unfolding order used

See also

measure_fold() to reconstruct the nD structure

Examples

# Create a 2D measurement (3 x 4 grid)
m2d <- new_measure_nd_tbl(
  location_1 = rep(1:3, each = 4),
  location_2 = rep(1:4, times = 3),
  value = 1:12,
  dim_names = c("time", "wavelength")
)

# Unfold to 1D
m1d <- measure_unfold(m2d)
m1d
#> <measure_tbl [12 x 2]>
#> # A tibble: 12 × 2
#>    location value
#>       <int> <int>
#>  1        1     1
#>  2        2     5
#>  3        3     9
#>  4        4     2
#>  5        5     6
#>  6        6    10
#>  7        7     3
#>  8        8     7
#>  9        9    11
#> 10       10     4
#> 11       11     8
#> 12       12    12

# Reconstruct
m2d_restored <- measure_fold(m1d)