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fix(3d-ngldm): DCNU/DCNUN summed the wrong marginal (== GLNU) #387

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fix(3d-ngldm): DCNU/DCNUN summed the wrong marginal (== GLNU) #387

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19 changes: 12 additions & 7 deletions src/nyx/features/3d_ngldm.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -305,17 +305,22 @@ void D3_NGLDM_feature::calc_features(const std::vector<double>& Sg, const std::v
f_GLNUN += sj * sj; // Grey Level Non Uniformity Normalised
}

for (int i = 0; i < Ng; ++i)
// FIX (bug): DCNU/DCNUN summed the GREY-LEVEL (row) marginal s_{i.}=sum_j s_ij (outer loop over i,
// inner sum over j) -- byte-identical to the GLNU loop above, so DCNU==GLNU always. DCNU is the
// DEPENDENCE-COUNT (column) marginal: s_{.j}=sum_i s_ij, then sum_j s_{.j}^2. Transpose the loops
// (outer over dependence-count columns j, inner sum over grey levels i), matching the row-marginal's
// j in [1,Nr) convention. (The 2D twin ngldm.cpp is already correct via separate Sg/Sr arrays.)
for (int j = 1; j < Nr; ++j) // FIX: outer loop is now the dependence-count column j
{
// Aggregate nonzero dependencies at each grey level
double si = 0;
for (int j = 1; j < Nr; ++j) // note: j \in [1,Nr) due to considering only nonzero dependencies
// Aggregate over grey levels at each dependence count
double scol = 0; // FIX: column marginal s_{.j}
for (int i = 0; i < Ng; ++i) // FIX: sum over grey levels i
{
double sij = NGLDM.yx(i, j);
si += sij;
scol += sij;
}
f_DCNU += si * si; // Dependence Count Non Uniformity
f_DCNUN += si * si; // Dependence Count Non Uniformity Normalised
f_DCNU += scol * scol; // FIX: Dependence Count Non Uniformity = sum_j s_{.j}^2
f_DCNUN += scol * scol; // FIX: Dependence Count Non Uniformity Normalised
}

for (int i = 0; i < Ng; ++i)
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4 changes: 2 additions & 2 deletions tests/test_3d_coverage_common.h
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Expand Up @@ -392,8 +392,8 @@ static const std::map<std::string, std::vector<double>>& unvetted_3d_local_regre
{ "3NGLDM_DCENE", { 0.14348407632898436 } },
{ "3NGLDM_DCENT", { 5.2277449211654039 } },
{ "3NGLDM_DCM", { 13.485998122653307 } },
{ "3NGLDM_DCNU", { 115443.18172715895 } },
{ "3NGLDM_DCNUN", { 0.22575716076180957 } },
{ "3NGLDM_DCNU", { 85056.840050062572 } }, // FIXED: was 115443.18172715895 (== GLNU, a transposed-marginal bug in 3d_ngldm.cpp)
{ "3NGLDM_DCNUN", { 0.16633455892143026 } }, // FIXED: was 0.22575716076180957 (== GLNUN, same bug)
{ "3NGLDM_DCP", { 1 } },
{ "3NGLDM_DCV", { 86.17064428912758 } },
{ "3NGLDM_GLM", { 16.955115769712151 } },
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4 changes: 2 additions & 2 deletions tests/test_3d_ngldm_ibsi.h
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Expand Up @@ -18,8 +18,8 @@ static std::unordered_map<std::string, double> d3ngldm_GT{
{ "3NGLDM_HDHGLE", 20030.0 },
{ "3NGLDM_GLNU", 115443.0 },
{ "3NGLDM_GLNUN", 0.23 },
{ "3NGLDM_DCNU", 115443.0 },
{ "3NGLDM_DCNUN", 0.23 },
{ "3NGLDM_DCNU", 85056.8 }, // FIXED: was 115443 (== GLNU) -- transposed-marginal bug in 3d_ngldm.cpp
{ "3NGLDM_DCNUN", 0.166335 }, // FIXED: was 0.23 (== GLNUN), same bug
{ "3NGLDM_DCP", 1.0 },
{ "3NGLDM_GLM", 17.0 },
{ "3NGLDM_GLV", 190.0 },
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