SUPPORT VECTOR MACHINE-BASED METHOD FOR ANALYSIS OF SPECTRAL DATA
Support vector machines are used to classify data contained within a structured dataset such as a plurality of signals generated by a spectral analyzer. The signals are pre-processed to ensure alignment of peaks across the spectra. Similarity measures are constructed to provide a basis for comparison of pairs of samples of the signal. A support vector machine is trained to discriminate between different classes of the samples. to identify the most predictive features within the spectra. In a preferred embodiment feature selection is performed to reduce the number of features that must be considered.
1 . A method for classifying samples into one or more classes based upon spectral characteristics of the samples, the method comprising:
downloading raw spectra obtained from the samples into a storage device in data communication with a processor adapted for executing support vector machines,
aligning the raw spectra using the processor by constructing a similarity measure for comparing pairs of spectra with a baseline spectrum and, based upon the similarity measure, offsetting each example spectrum from the baseline to provide a set of aligned raw spectra;
training at least one support vector machine to discriminate between the plurality of different sample classes using the aligned raw spectra;
processing one or more live spectrum from a subject sample having an unknown characteristic using the trained at least one support vector machine to classify the subject sample as having one of the different characteristics; and
generating an output comprising an identification of the characteristic into which the subject sample is classified for display on a graphical display or for storage in the storage device.
2 . The method of claim 1 , wherein the baseline is derived from the raw spectral data after applying a baseline subtraction algorithm.
3 . The method of claim 2 , wherein the baseline subtraction algorithm finds a smooth line that follows the bottom of a curve within the baseline spectrum without rising into the peaks.
4 . The method of claim 1 , wherein the similarity measure is determined according to the relationship
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where x i and x 0 are feature vectors corresponding to peaks of an i th example spectrum and the baseline spectrum, respectively, and ∥x i ∥ is the l 1 norm,
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5 . The method of claim 1 , wherein the similarity measure is determined according to the relationship S(x i −x 0 )=∥x i −x 0 ∥ 2 2 , where x i and x 0 are feature vectors corresponding to peaks of an i th spectrum and the baseline spectrum, respectively.
6 . The method of claim 1 , wherein the processor is further adapted for executing a feature selection algorithm for identifying peaks within the plurality of spectra to select a subset of spectral peaks that discriminate between the different classes, wherein the feature selection algorithm is selected from SVM-recursive feature elimination and l 0 -norm minimization.