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Eclipsed for much of the 20th century by such tools as vector analysis and matrix algebra, quaternions have more recently enjoyed a renaissance.

A special phase is presented in Vector Analysis.

It is found by plotting the sector densities directionally as lines of thrust, proportioned according to the density in each sector, and using vector analysis to obtain a vector resultant, representing the density and direction of the net trend.

The arrows indicate direction only and their slants were obtained by vector analysis of the over-all sector densities.

Standard methods of vector analysis are then applied to find the vector resultant.