Wavelength subsetting fails if formula is passed as a variable

[GegznaV]

Original issue was:

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When I pass wavelength range as a variable, functions [ and [[ fail. If I pass the formula directly, no issue is present. Is it a bug or did I do something wrong?

suppressPackageStartupMessages(library(hyperSpec))

# Works
flu[, 1:2, min ~ 320]
#> hyperSpec object
#>    6 spectra
#>    2 data columns
#>    0 data points / spectrum
#> wavelength: lambda/nm [numeric]
#> data:  (6 rows x 2 columns)
#>    1. spc: I[fl]/"a.u." [matrix, array0]
#>    2. filename: filename [character] rawdata/flu1.txt rawdata/flu2.txt ... rawdata/flu6.txt

# Fails
wl_range <- min ~ 320
flu[, 1:2, wl_range]
#> Error in Re(from): non-numeric argument to function

^{Created on 2020-07-14 by the reprex package (v0.3.0)}

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For the subsequent valuable comments and discussion, see:

• https://github.com/cbeleites/hyperSpec/issues/212