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我常用的idl程序或函数名（留个备份，以待后用）
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- NAME: GETROT
; PURPOSE: Return the rotation and plate scale of an image from its FITS header
; EXPLANATION: Derive the counterclockwise rotation angle, and the X and Y scale
; factors of an image, from a FITS image header. The input parameter
; may be either a FITS image header or an astrometry structure (as
; obtained by extast.pro)
CALLING SEQUENCE: GETROT, Hdr, [ Rot, CDelt, /SILENT, DEBUG = ] or GETROT, Astr, Rot,CDelt...
(Calabretta & Greisen (2002, A&A, 395, 1077) FITs standard))
- NAME ADXY
PURPOSE:Use a FITS header to convert astronomical to pixel coordinates
; EXPLANAtion Use an image header to compute X and Y positions, given the RA and Dec (or longitude, latitude) in decimal degrees.
; CALLING SEQUENCE: ADXY, HDR ;Prompt for Ra and DEC
; ADXY, hdr, a, d, x, y, [ /PRINT, ALT= ] - XYAD
CALLING SEQUENCE: XYAD, HDR ;Prompt for X and Y positions ; XYAD, HDR, X, Y, A, D, [ /PRINT, /Galactic, /Celestial, /Ecliptic, ; ALT =, PRECISION=]
3. ARROW: The ARROW procedure draws one or more vectors with arrow heads.
ARROW, X0, Y0, X1, Y1 [, /DATA | , /NORMALIZED] [, HSIZE=length] [, COLOR=index] [, HTHICK=value] [, /SOLID] [, THICK=value]
Note: you should use the plot first the arrow can work.
EG: plot, X0, YO, psym = 3, symsize =2, xtitle = 'RA(d)', ytitle = 'DEC(d)'
arrow, ........
HSIZE :是关于箭头大小的参数，可设 50-100.
3.The ROUND function rounds the argument to its closest integer Result = ROUND(X [, /L64 ] )
The CURVEFIT function uses a gradient-expansion algorithm to compute a non-linear least squares fit to a user-supplied function with an arbitrary number of parameters. The user-supplied function may be any non-linear function where the partial derivatives are known or can be approximated. Iterations are performed until the chi square changes by a specified amount, or until a maximum number of iterations have been performed. The CURVEVIT function returns a vector of values for the dependent variables, as fitted by the function fit.
Result = CURVEFIT( X, Y, Weights, A [, Sigma] )
For instrumental (Gaussian) weighting, set Weights i = 1.0/standard_deviation( Y i ) 2 . For statistical (Poisson) weighting, Weights i = 1.0/ Y i . For no weighting, set Weights i = 1.0.
A vector with as many elements as the number of terms in the user-supplied function, containing the initial estimate for each parameter. On return, the vector A contains the fitted model parameters. If A is double-precision, calculations are performed in double-precision arithmetic, otherwise they are performed in single-precision arithmetic.
A named variable that will contain a vector of standard deviations for the elements of the output vector A .
Smooth The SMOOTH function returns a copy of Array smoothed with a boxcar average of the specified width. The result has the same type and dimensions as Array. The algorithm used by SMOOTH is:
smooth funcation
https://blog.sciencenet.cn/blog-568426-494961.html
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