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*   Adding External Spectrum to a Projection
The objective of principal component projections of mass spectra is to find classes of compounds with common or similar properties. You can then use sufficiently separated classes to investigate the class membership of an unknown spectrum (see Example Workflow). Use the Spectra Projector window to add an external spectrum, which was not used for classification, to the projection plane. When the added spectrum is clearly projected into a particular class region, you can assume that this compound has similar, usually structural, properties.
The following figure shows that two groups are separated into clusters. You can add the unknown spectrum to the projection plane by pasting or opening its spectrum in a Spectra Projector window. The projection of this external spectrum shows that it belongs to the nicotine class (squares, PCA; or triangles, Fuzzy Clustering). You can confirm or reject this result using the fragmentation pattern of nicotine.
Nicotine and caffeine separated into clusters

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Related Topics:
  Generating a Spectra Projector Window
  Working in the Spectra Projector Window
  Using 3-D Projection Mode
  Opening and Saving Classification Results
  Accessing Spectra from a Spectra Projector Window
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