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*   Organizing Spectra
Spectra are organized into groups that can have their own names and graphic representations. When spectra are organized into groups, you can distinguish between the classes of spectra that should arise from the submitted groups of spectra after the classification process.
You can use the Mass Frontier application for the classification of spectra according to physical or chemical properties (point of origin, toxicity, aromaticity, and so on). For spectra that cannot be found in a library, classification can involve identification of substructure types or compound classes (structure elucidation) to establish and confirm structural proposals. Classification can also be useful in cases when you must retrieve only structurally related compounds from a complex chromatogram (metabolite research).
In classification analysis, distinguishing between two terms, groups and classes, is important. You can assign classes only after the classification method (Principal Component Analysis, Fuzzy Clustering, or Neural Networks (SOM)) clearly shows the occurrence of clusters or regions that consist of spectra with the desired properties. Before classification, you can only allocate spectra to groups according to preselected criteria. Often the objective of the classification process is to obtain classes that closely resemble groups of spectra submitted to classification.
You can save and open records with the .ref file extension, which are present in the Database Manager spreadsheet. This feature is especially useful for maintaining groups of spectra that are sent from the Database Manager to the Spectra Classifier window.
When you have retrieved spectra for classification, you might want to save these records, rather than save the spectra as ASCII files, such as JCAMP-DX (.jdx) or NIST MSP (.msp) files. In contrast to .jdx or .msp files, a reference file stores the locations where all the relevant information about each spectrum is saved (spectrum, structure, experimental conditions, and so on). These files are easy to manipulate; you can add or remove one or more records to them. You cannot save deconvoluted spectra from the Chromatogram Processor window as records (see Working with Detected Components).

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Related Topics:
  Classification Methods Background
  Advantages of Classification Methods in the Mass Frontier System
  Spectra Classification Methods
  Working in the Spectra Classifier Module
  Example Workflow
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