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diff --git a/noao/onedspec/doc/sinterp.hlp b/noao/onedspec/doc/sinterp.hlp new file mode 100644 index 00000000..b983beba --- /dev/null +++ b/noao/onedspec/doc/sinterp.hlp @@ -0,0 +1,146 @@ +.help sinterp Mar92 noao.onedspec +.ih +NAME +sinterp -- Interpolate a tables of x,y pairs to produce a spectrum +.ih +USAGE +sinterp tbl_file +.ih +PARAMETERS +.ls tbl_file +The name of a file which contains the x,y pairs to be used as +the basis for interpolation. The pairs must be in order of +increasing x. +.le + +The following parameters may or may not be necessary, depending +on the options selected. + +.ls input +If a few single elements are desired, rather than a full +array of elements, the user may enter a sequence of x values +from the terminal or a file to be used to interpolate into +the x,y table (parameter curve_gen=no). +.le +.ls image +If parameter make_image=yes, then an image file name is needed +.le +.ls order = 5 +If the interpolator is a polynomial fit or spline (interp_mode= +chebyshev, legnedre, spline3, spline1), the order of the fit +is required. +.le +.ls x1 +If parameter curve_gen=yes, this is the starting x value to +begin the curve generation. +.le + +Of the following three parameters, two must be specified, and the +third will be derived. + +.ls x2 = 0.0 +As above, but x2 determines the endpoint of the curve. +.le +.ls dx = 0.0 +As above, but dx determines the pixel-to-pixel increment +to be used during the curves generation. +.le +.ls npts = 0 +As above, but this determines the number of pixels to be generated. +.le + +.ls curve_gen = no +If this parameter is set to yes, then parameters x1, and two of +the three x2, dx, npts are required. The output is in the form +of new x,y pairs and may be redirected to a text file. +But if parameter make_image is also yes, the output is +in the form of an IRAF image file having the name given by +the parameter image. If curve_gen=no, the user must supply +a set of x values and interpolation is performed on those values. +.le +.ls make_image = no +If set to yes, then curve_gen=yes is implied and an image file name +is requied. A one dimensional IRAF image is created. +.le +.ls tbl_size = 1024 +This parameter defines the maximum size to be set aside for +memory storage of the input x,y pairs. +.le +.ls interp_mode = "chebyshev" +This parameter controls the method of interpolation. The linear +and curve options are true interpolators, while chebyshev, +legendre, spline3, and splin1 are fits to the data. +.le +.ih +DESCRIPTION +The specified file is read assuming it is a text file containing +pairs of x,y values in the form: xxx yyy. The table is used +to define the function y(x). The pairs must be entered in the file +in increasing order of x. + +The user specifies either specific x values for which the function +is to be evaluated, or specifies that a sequence of values beginning +with x1 are to be generated. In the former case, the explicit x values +may come either from the keyboard or from a file. In the latter case +the user must also specify the sequence by defining the increment, dx, +the endpoint, x2, and the number of points to generate in the sequence. +Then y(x) is evaluated at x1, x1+dx, x1+2*dx, ... , x1+(n-2)*dx, x2. +Only 2 of the 3 parameters (x2, dx, npts) are needed to fully +specify the sequence. + +The output of the function evaluation is either new x,y pairs written +to STDOUT, or an IRAF image. + +The function used to evaluated the tabular data may be any of the following +forms: + +.ls (1) +Linear interpolation between points. +.le +.ls (2) +Smooth interpolation between points. +.le +.ls (3) +A polynomial fit of either Legendre or Chebyshev types. +.le +.ls (4) +A cubic or linear spline. +.le + +If the table of x,y pairs is very large, the parameter tbl_size +should be set to the number of pairs. For example, if a spectrum +is available as a text file of x,y pairs (such as might be +obtained from IUE), and the number of pairs is 4096, then tbl_size +should be set to 4096. This provides for sufficient memory to +contain the table. + +.ih +EXAMPLES +The following shows how a text file may be used to generate a spectrum: + +.nf + cl> sinterp textfile make+ x1=4000 x2=5000 npts=1024 \ + >>> image=testimage interp_mode=curve +.fi + +The following sequence shows how to generate a spectrum of an IRS +standard star using the calibration file data as the source. + +.nf + cl> lcalib flam feige34 caldir=onedstds$irscal/ >textfile + cl> sinterp textfile make+ x1=3550 dx=1.242 npts=1024 \ + >>> interp_mode=linear image=feige34 +.fi +.ih +REVISIONS +.ls SINTERP V2.10.3+ +The image header dispersion coordinate system has been updated to the +current system. +.le +.ls SINTERP V2.10 +This task is unchanged. +.le +.ih +SEE ALSO +lcalib +.endhelp |