Professor Arthur T. Johnson
CURVEFIT uses a Gaussian elimination scheme to calculate least-squares coefficients to linearized equation forms. Linearization is accomplished with single keystrokes which cause transformation of data. New variables may be created, for example, to combine primary variables into new forms, or to form polynomial equations from simple two-variable input data. Useless variables may be removed. Errors such as dividing by zero, or taking logarithms of negative numbers are detected and prevented. The user may remove offending data values by reconsideration of the data.
FILTER uses the bilinear transformation with frequency prewarping to form a digital filter from an analog filter specified by the user. The user is required to choose among lowpass, highpass, bandpass, and bandstop filter types, and between Butterworth and Chebyshev filter families. To assist in these choices, some basic information is provided should the user require it. The number of filter poles must be chosen by the user, but an elaborate nomographic design aid is provided should it be required. Other filter parameters are requested by the program.