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STK_LINREG

STK_LINREG

Name


      STK_LINREG

Purpose


      Fit line by linear regression to columns in a stack of images.

Category


Calling Sequence


      stk_linreg, xx, yy, m, b, r2

Inputs


      xx = x values for each pixel in stack (3-D). in
      yy = stack of images (3-D). in

Keyword Parameters


Outputs


      m = Slope of fit for each column in stk (2-D). out
      b = y-intercept of fit for each column in stk (2-D). out
      r2 = Correlation coeficient for each column (2-D). out

Common Blocks


Notes


      Notes: yy is a stack of images. So it is a 3-D array.
      xx is the corresponding 3-D array that gives the x value
      for each image pixel. Let each image have size nx by ny,
      and let there be nz images. Then to generate an xx array
      that is the index of each image do the following:
        t = reform(findgen(nz),1,1,nz) ; Make a single column of indices.
        xx = rebin(t,nx,ny,nz,/samp) ; Now make full 3-D indices.
     
      Reference: http://mathworld.wolfram.com/LeastSquaresFitting.html
     

Example


          nx=5 & ny=8 & nz=10 ; Dimensions of stack.
          t = reform(findgen(nz),1,1,nz) ; Column of indices.
          xx = rebin(t,nx,ny,nz,/samp) ; Full index array.
          yy = xx*27 + 73 + randomu(k,nx,ny,nz)*30 ; Make a noisy line.
          stk_linreg,xx,yy,m,b,r2 ; Do fits.
          hlp,m,b,r2 ; Check.
          ; 1 Float array (5, 8). Min = 25.2887, Max = 28.7566
          ; 2 Float array (5, 8). Min = 76.2687, Max = 98.0477
          ; 3 Float array (5, 8). Min = 0.982812, Max = 0.995149
          plot,xx(2,3,*),yy(2,3,*),psym=-2
          x = findgen(10)
          oplot,x,x*m(2,3)+b(2,3),col=255

Modification History


      R. Sterner, 2004 Jan 27
  Copyright (C) 2004, Johns Hopkins University/Applied Physics Laboratory
  This software may be used, copied, or redistributed as long as it is not
  sold and this copyright notice is reproduced on each copy made. This
  routine is provided as is without any express or implied warranties
  whatsoever. Other limitations apply as described in the file disclaimer.txt.



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