Evaluates polynomial coefficients, such as those generated by POLYFIT, at the specified X values.
POLYGRAPH(coef, xdata, xy, form)
coef 
 
A series, the polynomial coefficients.  
xdata 
 
A series, the X values used to evaluate the polynomial.  
xy 
 
Optional. An integer, the series output form:  


 
form 
 
Optional. An integer, the polynomial coefficient form:  


A series, the value of the polynomial for the input xdata.
W1: gline(100,.01,1.0,1.0)^3
W2: polyfit(W1, 3)
returns a 4 point series with values {1,3,3,1} as the resulting 3^{rd} order coefficients
W3: polygraph(W2, xvals(w1))
graphs the fit.
Given the coefficient series a of an N^{th} order POLYFIT, if y[j] is the j^{th} point of the series generated by POLYGRAPH, then:
where a[k] is the k^{th} point in the coefficient series, and x[j] is the j^{th} point of the x series.
If form is 1, then:
If xy is 0, the result is an interval series where the XOFFSET is set to the first point of the X series and the DELTAX is set to the difference of the first two points in the X series.
If xy is 1, the result is an XY series where the X values are the same as xdata.
POLYGRAPH requires a series for the X data and always returns a series. See POLYVAL for a similar routine that accepts a scalar input and returns a scalar.
See POLYFIT to perform a least squares fit to generate polynomial coefficients.