Update README.md

Author: hanyoseob

README.md

@@ -20,16 +20,16 @@ X-ray computed tomography (CT) has experienced an explosion of technological dev
         * ![eq-line-integration](http://latex.codecogs.com/gif.latex?%5Cdpi%7B150%7D%20%5Cbg_white%20%5Cfn_cm%20%5Clarge%20p%28t%2C%5Ctheta%29%20%3D%20%5Cint_%7B-%5Cinfty%7D%5E%7B+%5Cinfty%7Df%27%28t%2Cs%29%20ds)
 
 ## Filtering
-* Filtering operator is implemented based on Ch.3 Equations (3.28) & (3.29) & (3.30).
+* Filtering operator is implemented based on Ch.3 Equations (3.21) & (3.29) & (3.30).
 
-* `Filtering kernel` is generated by Equation (3.29).
-    * ![eq-filtering-kernel](http://latex.codecogs.com/gif.latex?%5Cdpi%7B150%7D%20%5Cbg_white%20%5Cfn_cm%20%5Clarge%20h%28n%5Cdelta%29%20%3D%20%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20%5Cfrac%7B1%7D%7B4%5Cdelta%5E2%7D%2C%20%26%20n%3D0%2C%7E%7E%7E%5C%5C%200%2C%20%26%20n%3Deven%2C%5C%5C%20-%20%5Cfrac%7B1%7D%7B%28n%5Cpi%5Cdelta%29%5E2%7D%20%2C%20%26%20n%3Dodd.%7E%20%5Cend%7Bmatrix%7D%5Cright.)
+    * Ch.3 Equation (3.29): `Filtering kernel`
+        * ![eq-filtering-kernel](http://latex.codecogs.com/gif.latex?%5Cdpi%7B150%7D%20%5Cbg_white%20%5Cfn_cm%20%5Clarge%20h%28n%5Cdelta%29%20%3D%20%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20%5Cfrac%7B1%7D%7B4%5Cdelta%5E2%7D%2C%20%26%20n%3D0%2C%7E%7E%7E%5C%5C%200%2C%20%26%20n%3Deven%2C%5C%5C%20-%20%5Cfrac%7B1%7D%7B%28n%5Cpi%5Cdelta%29%5E2%7D%20%2C%20%26%20n%3Dodd.%7E%20%5Cend%7Bmatrix%7D%5Cright.)
 
-* Filtering is performed by `convolution ver.` using Ch.3 Equation (3.30) and `FFT ver.` using Equation (3.28).
+* Filtering is performed by `convolution ver.` using Ch.3 Equation (3.30) and `FFT ver.` using Equation (3.21).
     * Ch.3 Equation (3.30): `convolution ver.` 
         * ![eq-convolution](http://latex.codecogs.com/gif.latex?%5Cdpi%7B150%7D%20%5Cbg_white%20%5Cfn_cm%20%5Clarge%20f%28x%2Cy%29%3D%5Cint_%7B0%7D%5E%7B%5Cpi%7Dd%5Ctheta%5Cint_%7B-t_%7Bm%7D%7D%5E%7B+t_%7Bm%7D%7D%7Bp%28t%27%2C%20%5Ctheta%29h%28t-t%27%29dt%27%7D)
-    * Ch.3 Equation (3.28): `FFT ver.`
-        * ![eq-FFT](http://latex.codecogs.com/gif.latex?%5Cdpi%7B150%7D%20%5Cbg_white%20%5Cfn_cm%20%5Clarge%20g%28n%5Cdelta%2C%5Ctheta%29%3D%5Cdelta%5Csum_%7Bk%3D0%7D%5E%7BN-1%7D%7Bh%28n%5Cdelta-k%5Cdelta%29p%28k%5Cdelta%2C%20%5Ctheta%29%2C%7D%7E%7En%3D0%2C1%2C%5Ccdots%2CN-1)
+    * Ch.3 Equation (3.21): `FFT ver.`
+        * ![eq-FFT](http://latex.codecogs.com/gif.latex?%5Cdpi%7B150%7D%20%5Cbg_white%20%5Cfn_cm%20%5Clarge%20g%28t%2C%5Ctheta%29%20%3D%20g%28x%20%5Ccos%28%5Ctheta%29%20+%20y%20%5Csin%28%5Ctheta%29%29%20%5C%5C%5C%5C%20%7E%7E%7E%7E%7E%7E%7E%7E%7E%7E%7E%7E%7E%3D%20%5Cint_%7B-%5Cinfty%7D%5E%7B+%5Cinfty%7DP%28%5Comega%2C%5Ctheta%29%7C%5Comega%7C%20e%5E%7Bj2%5Cpi%5Comega%28x%5Ccos%28%5Ctheta%29%20+%20y%20%5Csin%28%5Ctheta%29%29%7D%20d%5Comega)
 
 ## Backprojection
 * Backprojection operator is implemented based on Ch.3 Equation (3.22).

lib/filtering.m

@@ -1,6 +1,6 @@
 % Please read the Ch. 3 Image Reconstruction
 
-% Implementation for filtering operator based on Ch. 3 Equation (3.29) & (3.30)
+% Implementation for filtering operator based on Ch. 3 Equation (3.21) & (3.29) & (3.30)
 % Filtering operator is implemented by both convolution and FFT versions.
 function [pdFltY, pdFlt] = filtering(pdY, param)
 
@@ -18,7 +18,7 @@
         end
 
     case 'fft'
-        % Ch.3 Equation (3.28)
+        % Ch.3 Equation (3.21)
         % FFT ver.
         pdFltY_         = zeros(param.nDctX, 1);
 

lib/generate_filter.m

@@ -1,4 +1,5 @@
-
+% Ch.3 Equation (3.29)
+% Generate filter kernel
 function pdFlt = generate_filter(d, n)
 
 pdFlt = zeros(2*n - 1, 1);