error: vol = gquad6(fun,xlow,xhigh,ylow,yhigh) ==== Six Point by Six Point Double Integral Gauss Formula ==== This function determines the volume under an externally defined function fun(x,y) between limits xlow and xhigh and ylow and yhigh. The numerical integration is performed using a gauss integration rule. The integration is done with a six point Gauss formula which involves base points bpx, bpy and weight factors wfxy. The normalized interval of integration for the bp and wf constants is -1 to +1 (in x) and -1 to 1 (in y). The algorithm is structured in terms of a parameter nquad = 6 which can be changed to accommodate a different order formula.