This function sums up feature intensities per analyte_id.
THis is is useful when you have multiple features (e.g. adducts, isotopes, in-source fragments) or isomers that you want to combine into a single analyte intensity value, such as LPC sn1 and sn2 species.
NOTE: This is still an experimental function! It will overwrite the feature_id in the dataset and analysis metadata of featured that share same analyte_id. Currently the original feature_id is not backed up anywhere. Use with caution and check results carefully!
Details
Only raw signal variables are aggregated across the transitions of an analyte:
feature_intensity, feature_height and feature_area are summed, and
feature_rt is averaged. feature_fwhm and feature_width are set to NA
for merged analytes: the constituents are separate chromatographic peaks, so
no aggregate of their peak widths describes the merged quantity.
Summing transitions redefines feature_intensity, so all values derived
from the pre-merge intensities are invalidated and removed: normalized
intensities, concentrations, drift/batch correction results and QC metrics.
Re-run normalize_by_istd() and the quantitation/correction steps after
merging. A message reports this when such values were present.
A merged analyte inherits the feature metadata (feature_class,
feature_label, istd_feature_id) of its first constituent transition. A
warning is issued when the constituents disagree, since the value that wins is
then arbitrary – for istd_feature_id it silently decides which internal
standard the merged analyte is normalized against.
is_quantifier is not inherited but determined by the merge: the merged
analyte is a quantifier if any of its constituents is one. A quantifier
combined with either a qualifier or another quantifier therefore yields a
quantifier, whereas qualifiers merged among themselves remain a qualifier.