Evaluation of classifiers

Basic principles of probability theory and information theory are used in the next Chapters to define objective criteria for the evaluation of classifiers. All considerations are restricted to binary classifiers but most concepts can be easily extended to multicategory problems. 

Many objections against the usefulness of pattern recognition methods for chemical problems are legitimated because the statistical evaluation was performed unsatisfactorily in many papers. Further confusions result from a non-uniform terminology (Chapter 11.5). An objective mathematical evaluation of classifiers is an absolute necessary prerequisite to a further application to actual classification problems. 

A weighted a posteriori probability p was proposed for the evaluation of classifiers C2393. 

Only a very short introduction to some basic ideas of information theory C189, 410, 412, 417, 420, 427, 4303 is given here in order to define those terms which are used for the evaluation of classifiers. 

The standard transinformation R is not necessarily the maximum amount of information that can be obtained by a given classifier. The maximum amount R is called channel capacity C417, 4273. R would be obtained for a random sample of patterns with optimally adjusted a priori probabilities. Because the optimal a priori probabilities depend on the classifier, the channel capacity is not suitable for the evaluation of classifiers. The only useful starting point for the classification of unknown chemical patterns is to assume equal probabilities for all classes. 

The evaluation of the proposed algorithms for the classification of ultrasonic resonance spectra clearly indicated that an adequate classifier can in many practical cases be obtained by... 

A summary of the evaluation of carcinogenic risks to humans by the International Agency for Research on Cancer is given in Table 5.17 together with the lARC reference. lARC classify carcinogens into four groups thus ... 

Nonlinear Equations and Systems.—For solving a single nonlinear equation in a single unknown, methods may be classified as local and global. A local method aims at the evaluation of a single... 

Analytical procedures are classified as being compendial or non-compendial in character. Compendial methods are considered to be valid, but their suitability should be verified under actual conditions of use. To do so, one verifies several analytical performance parameters, such as the selectivity/specificity of the method, the stability of the sample solutions, and evaluations of intermediate precision. 

However, this section pursues particle size measurement and evaluates its importance (as well as density) for the purpose of classifying the suitability of powders for long-distance pneumatic conveying applications. Initially, an appreciation of the fundamentals and the existing powder classification techniques is required. 

The synthesis and biological evaluation of pyrrole macrocycles (i.e., porphyrins, expanded porphyrins, and calixpyrroles) and linear oligopyrroles comprise perhaps the largest body of work published each year that can be classified as pyrrole chemistry. Unfortunately, due to space limitations, the discussion of selected advances in this area could not be included. 

Finally, in presenting this broad spectrum, I do not offer an evaluation of the efficacy or viability of the agent classes or any of the individual agents. I have included agents classified by the military as obsolete along with those that are still considered a major threat. It is important to remember that while an agent may have been a failure on the battlefield, it could still be a very successful weapon in the hands of a terrorist. 

From investigations of the effect of emorfazone on liver drug-metabolizing enzymes, (3) has been classified as a phenobarbitone (phenobarbital)-type inducer of enzymes [65]. For results of clinical evaluations of emorfazone, see [66, 67],... 

Consider first the evaluation of terms not involving h functions. The diagrams may be classified according to their topology into... 

Classify as sensitizer— most sensitive for moderate to strong sensitizers selection of protective equipment evaluation of allergic reactions... 

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