875   double *derivative)  in DerivativeHistogram()  argument
885   derivative[0]=(-1.5*histogram[0]+2.0*histogram[1]-0.5*histogram[2]);  in DerivativeHistogram()
886   derivative[n]=(0.5*histogram[n-2]-2.0*histogram[n-1]+1.5*histogram[n]);  in DerivativeHistogram()
891     derivative[i]=(histogram[i+1]-histogram[i-1])/2.0;  in DerivativeHistogram()
1521     *derivative,  in OptimalTau()  local
1566   derivative=(double *) AcquireCriticalMemory(256*sizeof(*derivative));  in OptimalTau()
1574     DerivativeHistogram(zero_crossing[i].histogram,derivative);  in OptimalTau()
1575     DerivativeHistogram(derivative,second_derivative);  in OptimalTau()
1586   DerivativeHistogram(zero_crossing[i].histogram,derivative);  in OptimalTau()
1587   DerivativeHistogram(derivative,second_derivative);  in OptimalTau()
1591   derivative=(double *) RelinquishMagickMemory(derivative);  in OptimalTau()