Hough Transform source code explanation

I couldn't understand the following code's for loop.

What is the purpose of the for loop here?

Why is for iterating from 7 to 7?

And, why is num_peak = 3?

clc
close all
clear all

imageCaption = sprintf('scratchedImage.jpg');
inputOriginalImage = imread(imageCaption);
inputOriginalImageGrayscale = rgb2gray(inputOriginalImage);

completelyPreprocessedImage = Preprocessing( inputOriginalImage );

N = 12;

bandpassFilteredImage = BandpassFiltering(completelyPreprocessedImage, N);

[ROWS, COLS, k] = size(bandpassFilteredImage);

homomorphicFilteredImage = HomomorphicFiltering(bandpassFilteredImage, N);

num_peak=3;
length_line=[];

for n=7:7
    inputImageForHaughtTransform = bwareaopen( homomorphicFilteredImage(:,:,n),20);

      [houghtTransformMatrix, theta, rho] = hough(inputImageForHaughtTransform);

      imshow(houghtTransformMatrix,[],'XData',theta,
             'YData',rho,'InitialMagnification','fit');
      xlabel('\theta'), ylabel('\rho');
      axis on, axis normal, hold on;

      peaks  = houghpeaks(houghtTransformMatrix,3,'threshold',
               ceil(0.3*max(houghtTransformMatrix(:))));
      x = theta(peaks(:,2)); 
      y = rho(peaks(:,1));
      plot(x,y,'s','color','white');

      foundLinesInHoughOperation = houghlines(inputImageForHaughtTransform, 
                                              theta, rho, peaks,'FillGap',
                                              5,'MinLength',7);
      figure, imshow(completelyPreprocessedImage), hold on    

      MarkLines(foundLinesInHoughOperation, COLS, x, y);
  end

Answer 1

[Walter Roberson]

We do not know. The routines Preprocessing(), BandpassFiltering(), and HomomorphicFiltering() are not Mathworks routines, and they do not appear to be anywhere in a File Exchange contribution either. We do not know what they do.

http://blogs.mathworks.com/steve/2013/06/25/homomorphic-filtering-part-1/