Impute Missing Data Points

Replace NAs in the spectra matrix by interpolation. With less than 4 points available linear interpolation of the 2 neighbour points is used. For larger numbers of neighbour points, smoothing interpolation is performed by stats::smooth.spline().

spc.NA.approx(
  spc,
  neighbours = 1,
  w = rep(1, 2 * neighbours),
  df = 1 + .Machine$double.eps,
  spar = NULL,
  debuglevel = hy.getOption("debuglevel")
)

Arguments

spc	hyperSpec object with spectra matrix containing NAs
neighbours	how many neighbour data points should be used to fit the line
w, df, spar	see stats::smooth.spline()
debuglevel	see options()

Value

hyperSpec object

Author

Claudia Beleites

Examples

fluNA <- hyperSpec:::fluNA
spc.NA.approx(fluNA [, , min ~ 410], debuglevel = 1)
#> Warning: Spectra containing only NAs found. They will not be approximated.
#> hyperSpec object
#>    6 spectra
#>    3 data columns
#>    11 data points / spectrum
#> wavelength: lambda/nm [numeric] 405.0 405.5 ... 410 
#> data:  (6 rows x 3 columns)
#>    1. spc: I[fl]/"a.u." [matrix, array11] 27.15 NA ... 281.8287 + NA
#>    2. filename: filename [character] rawdata/flu1.txt rawdata/flu2.txt ... rawdata/flu6.txt 
#>    3. c: c / (mg / l) [numeric] 0.05 0.10 ... 0.3 
spc.NA.approx(fluNA [1, , min ~ 410], debuglevel = 2)
#> hyperSpec object
#>    1 spectra
#>    3 data columns
#>    11 data points / spectrum
#> wavelength: lambda/nm [numeric] 405.0 405.5 ... 410 
#> data:  (1 rows x 3 columns)
#>    1. spc: I[fl]/"a.u." [matrix, array11] 27.15000 32.34467 ... 44.25133 
#>    2. filename: filename [character] rawdata/flu1.txt 
#>    3. c: c / (mg / l) [numeric] 0.05 
spc.NA.approx(fluNA [4, , min ~ 410], neighbours = 3, df = 4, debuglevel = 2)
#> hyperSpec object
#>    1 spectra
#>    3 data columns
#>    11 data points / spectrum
#> wavelength: lambda/nm [numeric] 405.0 405.5 ... 410 
#> data:  (1 rows x 3 columns)
#>    1. spc: I[fl]/"a.u." [matrix, array11] 130.6637 139.9983 ... 185.6923 
#>    2. filename: filename [character] rawdata/flu4.txt 
#>    3. c: c / (mg / l) [numeric] 0.2