STYL: Correct difference variance formula (docs)

Correct error in difference variance formula as pointed out by @clarehchao. Additionally, fix an error in the exampleCT settings (enabled shape features erroneously listed as glcm features).
Ougenny · Sep 5, 2017 · 147c1c8 · 147c1c8
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commit 147c1c8
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Showing 2 changed files with 29 additions and 17 deletions.
diff --git a/examples/exampleSettings/exampleCT.yaml b/examples/exampleSettings/exampleCT.yaml
@@ -14,22 +14,7 @@ imageType:
   Wavelet: {}
 
 featureClass:
-  shape: ['Volume',
-          'SurfaceArea',
-          'SurfaceVolumeRatio',
-          'Sphericity',
-          'SphericalDisproportion',
-          'Maximum3DDiameter',
-          'Maximum2DDiameterSlice',
-          'Maximum2DDiameterColumn',
-          'Maximum2DDiameterRow',
-          'MajorAxis',
-          'MinorAxis',
-          'LeastAxis',
-          'Elongation',
-          'Flatness'] # Only enable these shape descriptors (disables redundant Compactness 1 and Compactness 2)
-  firstorder:
-  glcm:  # disable redundant Compactness 1 and Compactness 2 features by specifying all other shape features
+  shape:  # disable redundant Compactness 1 and Compactness 2 features by specifying all other shape features
     - 'Volume'
     - 'SurfaceArea'
     - 'SurfaceVolumeRatio'
@@ -44,6 +29,33 @@ featureClass:
     - 'LeastAxis'
     - 'Elongation'
     - 'Flatness'
+  firstorder:
+  glcm:  # Disable SumAverage by specifying all other GLCM features available
+    - 'Autocorrelation'
+    - 'JointAverage'
+    - 'ClusterProminence'
+    - 'ClusterShade'
+    - 'ClusterTendency'
+    - 'Contrast'
+    - 'Correlation'
+    - 'DifferenceAverage'
+    - 'DifferenceEntropy'
+    - 'DifferenceVariance'
+    - 'Dissimilarity'
+    - 'JointEnergy'
+    - 'JointEntropy'
+    - 'Homogeneity1'
+    - 'Homogeneity2'
+    - 'Imc1'
+    - 'Imc2'
+    - 'Idm'
+    - 'Idmn'
+    - 'Id'
+    - 'Idn'
+    - 'InverseVariance'
+    - 'MaximumProbability'
+    - 'SumEntropy'
+    - 'SumSquares'
   glrlm:
   glszm:
 

diff --git a/radiomics/glcm.py b/radiomics/glcm.py
@@ -481,7 +481,7 @@ def getDifferenceVarianceFeatureValue(self):
 
     .. math::
 
-      \textit{difference variance} = \displaystyle\sum^{N_g-1}_{k=0}{(1-DA)^2p_{x-y}(k)}
+      \textit{difference variance} = \displaystyle\sum^{N_g-1}_{k=0}{(k-DA)^2p_{x-y}(k)}
 
     Difference Variance is a measure of heterogeneity that places higher weights on
     differing intensity level pairs that deviate more from the mean.