DOE-2 Reference Manual Version 2.1 - DOE2.com

108Z642Fig. IV.17.00 2 4 6 8 10XDefining a linear curve.The user must specify the form of the new curve. A bi-linear curve maybe pictured as a plane in three dimensions; it has the form z = a + bx + dy,*where the dependent variable, z, depends on two independent variables, x and y,A quadratic equation has the form z = a + bx + cx2, and will be graphed as aparabola. A bi-quadratic equation has the form z = a + bx + cx 2 + dy +cy2 + fxy, and it ma be Plctured as a curved surface. A cubic is of theform z = a + bx + cx 2 + dx and may be graphed as a curve with oneinflection point, a maximum, and a minimum.U-nameCURVE-F ITTYPEis a mandatory entry for this command.informs the SOL or POL processor that the data to follow define aparticular curve. A maximum of 100 CURVE-FIT instructions may beentered in DOE-2. If CURVE-FIT is run with DIAGNOSTIC = COMMENTS,an output listing of the curve coefficients, input or calculated,will be printed.specifies the form of the curve, and takes one of the followingcode-words as an input value.LINEAR means that if the data are given with the DATA keywordthey are to be fit to a linear equation in which there is onedependent variable, z, and one independent variable, x. If thedata are given with the COEFFICIENTS keyword, they will betreated as coefficients of the equation. The curve, actually aline, will have the form z = a + bx, where the coefficients are aand b (see Fig. IV.17).BI-LINEAR means that if the data that follow are given with theDATA keyword, they are to be fit to a bi-linear equation, one inwhich there is one dependent variable, z, and there are twoindependent variables, x and y. If the data are given with theCOEFFICIENTS keyword, they will be treated as coefficients of theequation. The curve will have the form z = a + bx + dy,* andgraphically it is represented by a plane. The coefficients area, b, and d.*A bi-linear curve is treated by the program as a bi-quadratic with zerocoefficients on the x 2 , y2, and xy terms, that is z = a + bx + Ox 2 +dy + ·Oy2 + Oxy. If TYPE is defined as bi-linear, therefore, and fourcoefficients are input, the first, second, and fourth coefficients will beused. However, only three coefficients need be input. To indicate this weare using the coefficient "d" on the y term.IV.181 (Revised 5/81)