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diff --git a/pkg/utilities/doc/polyfit.hlp b/pkg/utilities/doc/polyfit.hlp new file mode 100644 index 00000000..c9c01a8f --- /dev/null +++ b/pkg/utilities/doc/polyfit.hlp @@ -0,0 +1,91 @@ +.help polyfit Nov87 utilities +.ih +NAME +polyfit -- fit a polynomial to sets of data +.ih +USAGE +polyfit filelist order +.ih +PARAMETERS +.ls \fBfilelist\fR +File containing X,Y, SIGMAY triples to be fit. May be STDIN, or a list +of file names. Note that the third list quantity is only required if +\fIweighting\fR = instrumental. +.le +.ls \fBorder\fR +The order of the polynomial fit. (e.g. a parabolic fit has order 2) +.le +.ls weighting = uniform +The type of weighting for the fit. The choices are: +.ls uniform +No weighting. +.le +.ls instrumental +The weight of each point is equal to 1. / SIGMAY ** 2. +.le +.ls statistical +The weight of each point is equal to 1. / Y. +.le +.le +.ls \fBverbose\fR = no +If \fBverbose\fR = yes, additional information about the fit is printed on +the standard output. +.le +.ls \fBlistdata\fR = no +If \fBlistdata\fR = yes, the only output will be the calculated values for the +X,Y pairs. This is useful as input to \fIgraph\fR. +.le +.ih +DESCRIPTION +A polynomial weighted fit of specified order is fit to the X,Y, SIGMAY data +triples +read from the input file, files, or STDIN. The resulting coefficients +of the polynomial are printed on the first line of the standard output. +The uncertainty in each coefficient is printed on the next line. +These are listed as: + +.br +a0 a1 a2 a3 ... +.br +s0 s1 s2 s3 ... + +.br +where the polynomial has the form: + +.br +y = a0 + a1*x + a2*x**2 + a3*x**3 + ... + +.br +and the coefficients have uncertainties ("sigmas") s0 - sN. + +If verbose is set to yes, the following additional information is +listed: the resulting reduced chi-square, f-test, correlation coefficient, +standard deviation of residuals, and number of items in the list. +Also a tabular listing of each data element, X,Y, SIGMAY and the independent +variable, Yc, as calculated according to the fit, is printed. + +If listdata is set to yes, the only output which will appear will +be the listing of X,Yc,Y, SIGMAY. This provides a list suitable as input to +GRAPH or any other list oriented utility. Setting listdata to yes +overrides the verbose option. + +The routine REGRES from the library of routines written by Bevington is used +for the fit; see \fBData Reduction and Error Analysis\fR, by Bevington. +.ih +EXAMPLES + cl> polyfit STDIN 2 +.br + cl> polyfit datafile 4 verbose+ +.ih +BUGS +The maximum number of data elements is currently limited to 1000 +X,Y,SIGMAY triples. Also the system must be overdetermined. That is, the +number of data elements must exceed the order by at least 2. + +Beware of data elements having large dynamic range. The limitation +of the machine exponent range can produce overflow and underflow +arithmetic exceptions. +.ih +SEE ALSO +curfit +.endhelp |