**PURPOSE**- Fit a polynomial y=f(x) of degree < 6 to a set of x,y measurements stored in a document file. Evaluated polynomial points can be stored in a new document file.

**USAGE**- .OPERATION: PL FIT [a],[b],[c],[d]...

- .DOCUMENT FILE: DOC001

[Enter name of input document file.].FIRST, LAST KEY NUMBER: 4,45

[Enter first and last key under which the measurements are stored in the document file (it is not possible to leave gaps).].COLUMN #S FOR ABSCISSA, ORDINATE (0=KEY): 2,5

[Enter the columns where x and y are stored.].SCALEX, SCALEY (DEF=1): 10.5,1

[Enter the size of the x and y units. e.g. if the key is used for x each increment by 1 in the key could be an increment of 10.5 in x.].ORDER OF POLYNOMIAL (1-5, DEF=1): 3

[Enter the order of the polynomial that will be fitted to the data. In the example shown the polynomial a+bx+cx**2+dx**3 will be used. The output are the coefficients a,b,c,d. They are printed in the output and also stored in the (optional) register variables e.g. [a],[b],[c],[d]....].CREATE OUTPUT DOCUMENT FILE (Y/N): Y

[If Y is selected the polynomial is calculated over a specified range and stored as x, y pairs in a document file.] - If answer is 'Y' following questions appear:
- .X FROM, TO: 0.8, 30.7

[Enter range over which the polynomial is to be calculated. Note: the actual range has to be entered; SCALEX is not used for the calculation of the polynomial.].IN INTERVALS OF: 0.4

[Enter interval between the calculated points. Note: (XMIN-XMAX)/XIN = (TO-FROM)/INTERVAL+1 currently must not exceed 9999 because only 9999 value pairs can be stored in a document file.].DOCUMENT FILE: DOC002

[Enter name of output document file. The lines in this Document file will have the format:

KEY 2 x-value y-value. ]

**NOTES**

- Maximum order of polynomial reduced from 10 to 5 as the algorithm used sometimes fails beyond order 5. May 1999.

**SUBROUTINES**- POLLSQ, POLFIT

**CALLER**- PLOT1

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