DOE-2 Reference Manual Version 2.1 - DOE2.com

POOR PRACTICE GOOD PRACTICE GOOD PRACTICEFig. IV.18.Defining a quadratic curve.If TYPE = CUBIC, at least four points (four lists of values)must be input. If TYPE = BI-QUADRATIC, at least six points(six lists of values) must be input. To define- a bi-quadratic,the six points (six sets of three coordinates) must not all bein the same plane. If data points are input that, whengraphed, form two orthogonal (perpendicular) lines, the programwill incorrectly calculate the curve coefficients. This isbecause orthogonal lines determine a plane, and the user'scurve may not be planar. Also, as interpolation will be moreaccurate than extrapolation, the user should, if possible,input points that "bound" his area of interest (see figurebelow).Note that the first point entered is considered the design datapOint and shouTOlDe the most accurately known (e.g., either theARI point or that point in which the user has the highestconfidence). The program will force the curve to go throughthe first data point.AREA OF INTERESTAREA OF INTERESTAREA OF INTERESTPOOR PRACTICE POOR PRACTICE GOOD PRACTICEFig. IV.19.Defining a bi-quadratic curve.IV.183 (Revised 5/81)