VA F - Variance of reconstruction in Fourier space as function of frequency ||

(05/03/02)

PURPOSE

Compute the variance of a 3D reconstruction in Fourier space as a function of frequency.

SEE ALSO

USAGE

.OPERATION: VA F

.FIRST TEMPLATE FOR 2-D IMAGE NAME: IMG***
[This is normally a set of projections of a 3D reconstruction, see notes.]

.FILE NUMBERS OR SELECTION DOC. FILE NAME: 1-700
[Enter projection file numbers or the name of the document file containing projection file numbers in the first column.]

.SECOND TEMPLATE FOR 2-D IMAGE NAME: DATA***
[This is a set of 2D images used to calculate 3D reconstruction for which the variance in Fourier space is to be evaluated.]

.MASK FILE: MAS999
[Enter the name of mask image for masking each image in the set.]

.RING WIDTH: 0.5
[Enter ring width of each frequency radius for the variance computation.]

.DOCUMENT FILE: DOC001
[Enter name of resulting document file.]

NOTES

  1. If you do not want to mask the images, you still have to create a mask image with constant value 1 by using command 'MO'.

  2. The variance is calculated according to: VA(I) = SUM[(P(kx,ky) - D(kx,ky))^2]/(N-1)
    Sum over Fourier units in each ring of radius I

  3. Reference:
    P.A. Penczek. Variance in three-dimensional reconstructions from projections. In preparation.

SUBROUTINES

VARF, VARF1

CALLER

UTIL4
      ; Calculation of Fourier space variance
      BP 3F
      stack@*****
      1-799
      angles001
      *
      vol001

      ; Get the variance
      PJ 3Q
      vol001
      (35)
      1-799
      angles001
      prjn@***

      RF VAR
      dala@****
      1-799
      prjn@***
      1-799
      circle
      (1)
      variance

      EN

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