Authors: Hangting Ye, Peng Wang, Wei Fan, Xiaozhuang Song, He Zhao, Dandan Gun, Yi Chang
Organizations: School of Artificial Intelligence, Jilin University, China. · School of Computer Science, University of Auckland, New Zealand. · Chinese University of Hong Kong, Shenzhen, China. · CSIRO’s Data61 and Monash University, Australia. · Engineering Research Center of Knowledge-Driven Human-Machine Intelligence, Ministry of Education, China · International Center of Future Science, Jilin University, China.
Tabular data have been playing a mostly important role in diverse real-world fields, such as healthcare, engineering, finance, etc. The recent success of deep learning has fostered many deep networks (e.g., Transformer, ResNet) based tabular learning methods. Generally, existing deep tabular machine learning methods are along with the two paradigms, i.e., in-learning and pre-learning. In-learning methods need to train networks from scratch or impose extra constraints to regulate the representations which nonetheless train multiple tasks simultaneously and make learning more difficult, while pre-learning methods design several pretext tasks for pre-training and then conduct task-specific fine-tuning, which however need much extra training effort with prior knowledge. In this paper, we introduce a novel deep Tabular Representation Corrector, TRC, to enhance any trained deep tabular model's representations without altering its parameters in a model-agnostic manner. Specifically, targeting the representation shift and representation redundancy that hinder prediction, we propose two tasks, i.e., (i) Tabular Representation Re-estimation, that involves training a shift estimator to calculate the inherent shift of tabular representations to subsequently mitigate it, thereby re-estimating the representations and (ii) Tabular Space Mapping, that transforms the above re-estimated representations into a light-embedding vector space via a coordinate estimator while preserves crucial predictive information to minimize redundancy. The two tasks jointly enhance the representations of deep tabular models without touching on the original models thus enjoying high efficiency. Finally, we conduct extensive experiments on state-of-the-art deep tabular machine learning models coupled with TRC on various tabular benchmarks which have shown consistent superiority.
Figures & tables
Fig. 1 : The performance of deep tabular models with varying noise levels in observations. FT-Transformer, MLP, and DCN2 indicate different deep tabular models. For regression tasks, lower RMSE is better, and for classification tasks, higher accuracy is better.
Fig. 2 : The relation between model performance and the corresponding SVE values of representations. For each subfigure, we conduct experiment on multiple random seeds. We find that deep tabular models with higher SVE often yield lower performance.
Fig. 3 : The framework of Tabular Representation Corrector (TRC). Subfigure (a) illustrates the overall TRC framework, subfigure (b) presents the training process for the shift estimator of TRC, and subfigure (c) presents the training process for the coordinate estimator of TRC. Here, zi=Gf(xi;θf) is the output of any trained backbone. zi would be enhanced via two tasks. In subfigure (b), the explicitly perturbed samples are only used for training the shift estimator. During the test stage, we feed the representations extracted by the existing trained deep tabular model, which are from the test dataset (notably, we do not add any noise to the test dataset), into the shift estimator followed by the coordinate estimator to achieve the calibrated representations of test samples.
CO
DI
QS
CA
PO
SU
AD
AU
GE
YE
COV
Objects
9568
53940
908
20640
15000
21263
48842
690
9873
515345
581012
Numerical
4
6
6
8
48
81
6
14
32
90
54
Categorical
0
3
0
0
0
0
8
0
0
0
0
Classes
-
-
-
-
-
-
2
2
5
-
7
Metric
RMSE
RMSE
RMSE
RMSE
RMSE
RMSE
Accuracy
Accuracy
Accuracy
RMSE
Accuracy
TABLE I : Tabular data properties. “Objects” indicates the dataset size. RMSE denotes Root Mean Square Error for regression, Accuracy is used for binary and multiclass classification.
CO ↓
DI ↓
QS ↓
CA ↓
PO ↓
SU ↓
AD ↑
AU ↑
GE ↑
MLP (i)
3.961
564.373
0.875
0.505
10.892
10.379
0.856
0.870
0.578
+ TRC
3.899
558.330
0.825
0.502
10.593
10.326
0.858
0.891
0.580
DCN2 (i)
4.016
591.958
1.027
0.495
8.805
10.674
0.856
0.841
0.564
+ TRC
3.858
574.453
0.879
0.493
8.790
10.584
0.857
0.862
0.584
SNN (i)
11.789
1530.293
1.018
0.896
18.517
25.498
0.847
0.848
0.550
+ TRC
6.880
693.369
0.870
0.699
11.202
15.537
0.847
0.877
0.573
TABLE II : Results of overall performance. “i” denotes in-learning and “p” denotes pre-learning for baseline models. The best results are highlighted in bold. The improvement of TRC over baselines is statistically significant at the 95% confidence level.
Fig. 4 : Performance improvement of TRC over various backbone models on large scale datasets.
Backbone
TR
SC
DE
CO ↓
DI ↓
QS ↓
CA ↓
PO ↓
SU ↓
AD ↑
AU ↑
GE ↑
MLP
3.961
564.373
0.875
0.505
10.892
10.379
0.856
0.87
0.578
✓
3.916
563.649
0.868
0.502
10.605
10.328
0.858
0.87
0.571
✓
3.92
564.141
0.845
0.505
10.631
10.349
0.858
0.862
0.568
✓
✓
3.908
558.52
0.852
0.502
10.602
10.341
0.858
0.87
0.575
✓
✓
3.922
565.129
0.841
0.505
10.622
10.363
0.858
0.877
0.577
✓
✓
✓
3.899
558.33
0.825
0.502
10.593
10.326
0.858
0.891
0.58
TABLE III : Analysis on the effects of different components of TRC . The best results are highlighted in bold, and the second best results are underscored.
CO ↓
DI ↓
QS ↓
CA ↓
PO ↓
SU ↓
AD ↑
AU ↑
GE ↑
MLP
3.961
564.373
0.875
0.505
10.892
10.379
0.856
0.870
0.578
deeper MLP
3.942
562.888
0.871
0.510
11.583
10.471
0.856
0.862
0.572
MLP+ TRC
3.899
558.330
0.825
0.502
10.593
10.326
0.858
0.891
0.580
FT-Transformer
3.709
551.190
0.823
0.469
2.919
10.410
0.858
0.848
0.611
deeper FT-Transformer
3.704
559.363
0.816
0.474
2.890
10.442
0.851
0.856
0.613
FT-Transformer+ TRC
3.648
543.653
0.780
0.462
2.728
10.223
0.862
0.884
0.624
TABLE IV : Performance of backbone w/ TRC and deeper backbone. The depths of backbone layers are increased only for “deeper backbone”.
CO ↓
DI ↓
QS ↓
AU ↑
MLP (i)
3.961
564.373
0.875
0.870
+Linear Head
3.952
563.945
0.870
0.870
+Linear Head & Backbone
3.937
563.304
0.880
0.862
+MLP Head
3.950
562.076
0.862
0.870
+MLP Head & Backbone
3.934
562.427
0.857
0.870
+LoRA
3.941
563.314
0.875
0.870
TABLE V : Performance comparison between various fine-tuning paradigms and TRC. “i” denotes in-learning and “p” denotes pre-learning for baseline models.
Fig. 5 : Comparison of the L1 norm of the shift information estimated by TRC on data samples with different gradients. For each data sample, the gradient is computed by ∥∇θfL(x,y;θ)∥1 , where θ is the parameters of the trained deep tabular model. We partition the L1 norm of gradients into 10 equally spaced intervals from low to high and count the number of samples in each interval.
Fig. 6 : SVE and performance changes of backbone models w/ and w/o TRC on different datasets. Subfigures (a) and (c) show the Singular Value Entropy (SVE) (Eq. 3 ) of representation space w/ and w/o TRC on different datasets. Subfigures (b) and (d) show the corresponding performance.
CO ↓
DI ↓
AU ↑
Train
Val
Train
Val
Train
Val
MLP
3.961
3.968
564.373
565.616
0.870
0.870
+ TRC
3.902
3.899
559.020
558.330
0.891
0.891
FT-Transformer
3.709
3.726
551.190
550.228
0.848
0.848
+ TRC
3.647
3.648
544.570
543.653
0.877
0.884
TABLE VI : The influence of using a small portion (1%) of validation set for training. “Train” indicates only training data are used for training model, “Val” indicates additional small portion of validation data are used for training.
Fig. 7 : The results of TRC training with missing values and fewer samples. The left two subfigures indicate the scenarios with missing values, while the right two indicate the scenarios where the number of training samples is reduced.
Fig. 8 : The TSNE visualization of learned representations of deep tabular model, deep tabular model w/ FT (fine-tuning), deep tabular model w/ Task 1 (Tabular Representation Re-estimation) and deep tabular model w/ Task 1, 2 (Tabular Representation Re-estimation and Tabular Space Mapping) (i.e., TRC). Here, the backbone model is ResNet. The first row represents the CA dataset (regression), while the second row represents the GE dataset (classification). Different colors indicate different labels. Marker=“x” indicates embedding vectors.
Fig. 9 : The comparison of parameters between TRC and different deep tabular models. The parameters for TRC do not include the parameters for backbone models.
Fig. 10 : Comparison with different approximated optimal representation selection strategies across a wide range of threshold τ on CO dataset ↓ .
Fig. 11 : The performance of TRC with varying number of embedding vectors on CO dataset ↓ .
DI ↓
QS ↓
PO ↓
AU ↑
FT-Transformer+ TRC
543.653
0.780
2.728
0.884
CatBoost [ 9 ]
546.827
0.817
4.641
0.855
XGBoost [ 8 ]
559.680
0.820
4.936
0.862
TABLE VII : Comparison with tree-based methods.
Appendix figures & tables18 assets
Supplementary material from the paper’s appendix.
Appendix
Symbols
Description
x,y
Observed sample and the corresponding label.
N
Number of observed samples in a dataset.
Dtrain , Dval , Dtest
Training set, validation set, test set.
F(⋅;θ)
Deep tabular model.
Gf(⋅;θf)
Existing deep tabular backbone.
Gh(⋅;θh)
Prediction head.
Appendix
TABLE VIII : Notation.
TR
SC
DE
CA ↓
CO ↓
DI ↓
QS ↓
SU ↓
PO ↓
AD ↑
AU ↑
GE ↑
MLP
0.505
3.961
564.373
0.875
10.379
10.892
0.856
0.87
0.578
✓
0.502
3.916
563.649
0.868
10.328
10.605
0.858
0.87
0.571
✓
0.505
3.92
564.141
0.845
10.349
10.631
0.858
0.862
0.568
✓
✓
0.502
3.908
558.52
0.852
10.341
10.602
0.858
0.87
0.575
✓
✓
0.505
3.922
565.129
0.841
10.363
10.622
0.858
0.877
0.577
✓
✓
✓
0.502
3.899
558.33
0.825
10.326
10.593
0.858
0.891
0.58
Appendix
TABLE IX : Analysis on the effects of different components of TRC . The best results are highlighted in bold, and the second best results are underscored. This table serves as an extension of Table III in manuscript.
CO ↓
DI ↓
QS ↓
CA ↓
PO ↓
SU ↓
AD ↑
AU ↑
GE ↑
MLP
3.961
564.373
0.875
0.505
10.892
10.379
0.856
0.870
0.578
deeper MLP
3.922
562.888
0.851
0.510
11.583
10.271
0.856
0.862
0.572
MLP+ TRC
3.899
558.330
0.825
0.502
10.593
10.326
0.858
0.891
0.580
DCN2
4.016
591.958
1.027
0.495
8.805
10.674
0.856
0.841
0.564
deeper DCN2
3.872
575.765
0.904
0.486
9.165
10.675
0.858
0.862
0.575
DCN2+ TRC
3.858
574.453
0.879
0.493
8.790
10.584
0.857
0.862
0.584
Appendix
TABLE X : Performance of backbone w/ TRC and deeper backbone. The depths of backbone layers are increased only for “deeper backbone”. This table serves as an extension of Table IV in manuscript.
Fig. 12 : The results of TRC training with missing values. This figure serves as an extension of Fig. 7 in manuscript.
Fig. 13 : The results of TRC training with fewer samples. This figure serves as an extension of Fig. 7 in manuscript.
Fig. 14 : The comparison of parameters between TRC and deep tabular models. This figure serves as an extension of Fig. 9 in manuscript.
CO
DI
QS
CA
PO
SU
AD
AU
GE
YE
COV
MLP
0.129
0.719
0.013
0.267
0.189
0.285
0.566
0.011
0.123
9.259
9,442
TRC
0.171
0.878
0.020
0.348
0.248
0.372
0.688
0.017
0.167
13.086
13.818
ResNet
0.188
1.092
0.020
0.399
0.282
0.424
0.864
0.016
0.184
15.285
13.948
TRC
0.168
0.880
0.021
0.354
0.249
0.374
0.698
0.018
0.167
13.629
12.909
FT-Transformer
0.424
2.348
0.045
0.917
0.685
1.397
1.857
0.038
0.431
68.678
52.186
TRC
0.174
0.891
0.027
0.356
0.259
0.382
0.705
0.024
0.174
13.200
13.194
Appendix
TABLE XI : Time cost (seconds) per training epoch on the full training set. The training time for TRC does not include the training cost for backbone model.
CO
DI
QS
CA
PO
SU
AD
AU
GE
YE
COV
MLP
0.007
0.053
0.003
0.015
0.012
0.013
0.081
0.003
0.009
0.177
0.397
TRC
0.006
0.032
0.002
0.013
0.011
0.011
0.053
0.002
0.006
0.151
0.297
ResNet
0.016
0.111
0.006
0.042
0.030
0.034
0.147
0.006
0.020
0.433
0.970
TRC
0.005
0.033
0.002
0.015
0.010
0.012
0.043
0.002
0.006
0.154
0.341
FT-Transformer
0.042
0.275
0.012
0.130
0.131
0.180
0.512
0.012
0.083
2.704
4.600
TRC
0.005
0.030
0.001
0.014
0.010
0.012
0.051
0.001
0.007
0.142
0.318
Appendix
TABLE XII : Inference time cost (seconds) on the full test set. The inference time for TRC does not include the inference time for backbone model.
Fig. 15 : The TSNE visualization of coefficients for embedding vectors.
Fig. 16 : The visualization of the similarity matrix for embedding vectors on FT-Transformer.
Fig. 17 : The visualization of coefficients for embedding vectors.
Fig. 18 : Increasing the number of embedding vectors leads to larger SVE values of representations.
Fig. 19 : The performance of TRC with varying weights of the orthogonality loss.
Fig. 20 : The performance of TRC with varying times of perturbing the observation in Inherent Shift Learning.
Fig. 21 : The performance of TRC with the varying proportion of the selected optimal representation over all of the validation set samples, i.e., τ . This figure serves as an extension of Fig. 10 in manuscript.
Fig. 22 : The performance of TRC with varying number of embedding vectors. This figure serves as an extension of Fig. 11 in manuscript.
Backbone
Discrepancy ( ↓ )
AD
CA
CO
GE
MLP
w/o Shift Estimator
0.647
0.487
0.450
0.464
MLP
w/ Shift Estimator
0.578
0.395
0.246
0.434
FT-Transformer
w/o Shift Estimator
2.217
2.460
2.352
3.870
FT-Transformer
w/ Shift Estimator
1.068
0.887
0.820
1.443
Appendix
TABLE XIII : The L2 distance between sub-optimal representations and optimal representations w/o and w/ shift estimator. “w/o Shift Estimator” corresponds to the distance between zilight and ziheavy , “w/ Shift Estimator” corresponds to the distance between z^i and ziheavy .
Datasets
Backbone training epochs
DCN2
+ TRC (Lowest, ours)
+TRC (Random)
+TRC (Highest)
CO ↓
5%
4.57
4.498
4.512
4.503
CO ↓
50%
4.384
4.165
4.285
4.325
GE ↑
5%
0.508
0.527
0.525
0.524
GE ↑
50%
0.543
0.561
0.55
0.548
Appendix
TABLE XIV : The performance of TRC on underfitted backbone.
Natural Language Processing Lab, Soochow University, Suzhou, China · Ant Group, Hangzhou, China · The Hong Kong Polytechnic University, Hong Kong, China