PURPOSE: To provide the differential and the integral of discrete data for which (x) axis data form logarithmic intervals with accurately with the little amount of calculation by approximating a curve passing the discrete data with an n-th order equation. ;CONSTITUTION: A hardware is constituted of an amplifier and a frequency converter, etc., 1 for inputting analog signals (frequency data and level data,) an A/D converter 2, a memory 3, a CPU 4 for calculating the differential value and the integral value and a display device 5 for displaying the differential value and the integral value, etc. In this case, when the coordinate data of a point P0 for obtaining a partial value is (f, y0) the coordinate data of points P-1 and P1 on the both sides are indicated by (f/r, y-1) and (fr, y1). Then, the curve is indicated by the n(≥2)-th equation g(x) of (x), the equation g(x) is obtained by substituting the (x) axis data and the (y) axis data of the (n+1) pieces of consecutive points including the point for obtaining the differential value in between for the equation g(x), a differential equation dg(x)/dx is obtained and the (x) axis data of the point for obtaining the differential value is substituted for the differential equation.;COPYRIGHT: (C)1993,JPO&Japio
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