smix_by_names: create a new weighted spectrum with spectrum names
In iona5/spectramix: Create new spectra from other spectra

a convenience function to create a new spectrum from named weights. the weights can add up to 1 or 100 indicating a plain factor or percentages. if they add up to some other value, indicate via normalize = TRUE, that you want a normalization.

1	smix_by_names(data, weights_df, normalize = FALSE)

`data`	a data frame containing the spectra to mix. it is assumed the first column contains the Wavelength labels
`weights_df`	a 1-row data frame with the weights. the column names are the names of the spectra to be mixed from data. the row itself contains its weights
`normalize`	if the weights should be normalized