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diff --git a/pkg/utilities/doc/curfit.hlp b/pkg/utilities/doc/curfit.hlp new file mode 100644 index 00000000..df8be6fd --- /dev/null +++ b/pkg/utilities/doc/curfit.hlp @@ -0,0 +1,168 @@ +.help curfit Jun88 utilities +.ih +NAME +curfit -- fit a curve to a list or an image section +.ih +USAGE +curfit input +.ih +PARAMETERS +.ls input +The data to be fit. May be an image section, STDIN or a list of file names. +.le +.ls function = legendre +The type of function with which to fit the data. Choices are +legendre, chebyshev, spline1 (linear spline) or spline3 (cubic spline). +.le +.ls order = 4 +The order of the fit or number of spline pieces. +.le +.ls weighting = uniform +The type of weighting for the fit. The options are: +.ls uniform +The weight w = 1.0. This option may be used for both list input and image +input. +.le +.ls user +The weights are supplied by the user. This option may be used for list input +only. +.le +.ls statistical +The weight w = 1.0 / y. This option can be used for both list and image data. +.le +.ls instrumental +The user supplies the sigmay for each point and w = 1.0 / sigmay ** 2. +This option may be used for list input only. +.le +.le +.ls interactive = yes +If \fBinteractive\fR is set to yes, a plot of the fit is drawn and the +cursor is available for interactively examining and adjusting the fit. +.le +.ls axis = 1 +If \fBinput\fR names an image or image section, this parameter specifies +the axis along which the image is projected for fitting. +.le +.ls listdata = no +If \fBlistdata\fR is set to yes, the only printed output will be the calculated +values for the X,Y pairs. This is useful as input to \fIgraph\fR or some +other list oriented program. +.le +.ls verbose = no +If \fBverbose\fR is set to yes, the fitted (X,Y) pairs are listed in addition +to the default output of filename, function type, order, rejection parameters, +coefficients and their errors. +.le +.ls power = no +If \fBpower\fR is set to yes, the coefficients of the legendre or +chebyshev polynomials will be converted to power series coefficients. +.le +.ls calctype = "double" +Calculation datatype. The two datatypes are "real" (single precision) and +"double" (double precision). +.le +.ls device = "stdgraph" +The output device for interactive graphics. +.le +.ls cursor = "stdgcur" +The source of graphics cursor input. +.le +.ih +DESCRIPTION +A curve is fit to data read from either an image section or a list. +The type of curve is set by the \fBfunction\fR parameter as either +a legendre polynomial, chebyshev polynomial, linear spline or cubic +spline, with the order of the fit (or number of spline pieces) set by +\fBorder\fR. If data is read from an image, the \fBaxis\fR parameter +is used to reduce the dimensionality of the image; it specifies the +axis along which the image is projected. For example, when \fBaxis\fR += 1, the image is compressed to a column. \fBAxis\fR = 2 would project +the image along a line; \fBaxis\fR = 3 indicates projection in the z +direction, etc. + +The input data must be ordered in x because of a restriction in the +interactive plotting package. If the input is from a list, the data +are sorted prior to fitting; image input data are assumed to be ordered +in x and are not explicitly sorted by \fIcurfit\fR. + +If the input is from a list the user may specify a set of weights, +\fBweighting\fR = user or a set of errors, \fBweighting\fR = +instrumental. An additional weighting option \fBweighting\fR = statistical +can be used for both list and image data. The default is \fBweighting\fR = +uniform. + +When \fBinteractive\fR = yes, the curve is plotted and cursor commands allow +for interactive examining and adjustment of the fit. +The full range of interactive cursor commands is available +including those for changing the function type, order, and rejection criteria, +and examining the residuals. + +The final fit parameters are written to STDOUT with the +format controlled by parameters \fBverbose\fR and \fBlistdata\fR. +By default, the function type, order, and resulting chi-square are +printed as well as the coefficients and their standard deviations. +If \fBverbose\fR is set to yes, a list of X, Y_calculated, Y_input, +and W_input is also printed. +If \fBlistdata\fR is set to yes, the only printed output will +be a listing of X, Yc, Y and W. This provides a list suitable as input to +\fBgraph\fR or any other list oriented utility. Setting \fBlistdata\fR +to yes overrides the verbose option. + +When \fBpower\fR = yes, the coefficients are converted to power series +coefficients of the form a0 + a1*X + a2*X**2 +a3*X**3 .... +Only legendre and chebyshev coefficients are converted; a conversion +of spline coefficients is meaningless. Also, errors in the coefficients +are not converted. + +The user has a choice of single or double precision calculations. Generally +double precisions is used since the calculation time is only slightly +longer. The single precision calculation is used in many other tasks +which do many fits. This task provides a test tool to compare the +results between the two levels of precision. +.ih +EXAMPLES + +1. The x,y pairs in file test.data are interactively fit with a fourth +order legendre polynomial. The printed output is shown. + + cl> curfit test.data + +.nf + NOAO/IRAF V2.0 Hammond@lyra Fri 11:45:41 13-Dec-85 + file = test.data + function = legendre + grow = 0. + naverage = 1 + order = 4 + low_reject = 0., high_reject = 0. + niterate = 1 + sample = * + total points = 8 + sample points = 8 + nrejected = 0 + deleted = 0 + square root of reduced chi square = 3.008706E-6 + coefficient error + 1 2.633E1 1.098E-6 + 2 3.150E1 1.820E-6 + 3 8.167E0 1.896E-6 + 4 -1.621E-6 2.117E-6 + +.fi +2. Fit a cubic spline to the last 12 columns of image "m74". + + cl> curfit m74[501:512,1:512] axis=2 func=spline3 order=5 + +3. Use \fIcurfit\fR as a filter to overplot a smoothed curve to an existing +plot of the data points. The command line for \fBgraph\fR is shown as +well as the \fBcurfit\fR command. Note the interactive flag for +\fBcurfit\fR is turned off. + + cl> graph points.list point+ mark=box wx1=.13 xlab="X VALUES"\ + >>> ylab="Y VALUES" title="Legendre fit to points.list" + + cl> type points.list | curfit list+ inter- | graph append+ +.ih +SEE ALSO +icfit, polyfit +.endhelp |