Linear regression with combined L1 and L2 priors as regularizer. # distributed under the License is distributed on an "AS IS" BASIS. Hence, the optimization problem (19) can be simplified as. Regression Usage Model Recommendation Systems Usage Model Data Management Numeric Tables Generic Interfaces Essential Interfaces for Algorithms Types of Numeric Tables Data Sources Data Dictionaries Data Serialization and Deserialization Data Compression Data Model Analysis K-Means Clustering ... Quality Metrics for Multi-class Classification Algorithms Equation (26) is equivalent to the following inequality: From Linear Regression to Ridge Regression, the Lasso, and the Elastic Net. Fit multiclass models for support vector machines or other classifiers: predict: Predict labels for linear classification models: ... Identify and remove redundant predictors from a generalized linear model. PySpark's Logistic regression accepts an elasticNetParam parameter. In multiclass logistic regression, the classifier can be used to predict multiple outcomes. This completes the proof. By combining the multinomial likeliyhood loss and the multiclass elastic net penalty, the optimization model was constructed, which was proved to encourage a grouping effect in gene selection for multiclass … Linear, Ridge and the Lasso can all be seen as special cases of the Elastic net. holds for any pairs , . Hence, the following inequality Given a training data set of -class classification problem , where represents the input vector of the th sample and represents the class label corresponding to . For the microarray classification, it is very important to identify the related gene in groups. Hence, the regularized logistic regression optimization models have been successfully applied to binary classification problem [15–19]. Setup a grid range of lambda values: lambda - 10^seq(-3, 3, length = 100) Compute ridge regression: ml_logistic_regression (x, formula = NULL, fit_intercept = TRUE, elastic_net_param = 0, reg_param = 0, max_iter = 100 ... Thresholds in multi-class classification to adjust the probability of predicting each class. Besides improving the accuracy, another challenge for the multiclass classification problem of microarray data is how to select the key genes [9–15]. Logistic regression is used for classification problems in machine learning. that is, Meanwhile, the naive version of elastic net method finds an estimator in a two-stage procedure : first for each fixed λ 2 {\displaystyle \lambda _{2}} it finds the ridge regression coefficients, and then does a LASSO type shrinkage. Multinomial logistic regression is a particular solution to classification problems that use a linear combination of the observed features and some problem-specific parameters to estimate the probability of each particular value of the dependent variable. By combining the multinomial likelihood loss function having explicit probability meanings with the multiclass elastic net penalty selecting genes in groups, the multinomial regression with elastic net penalty for the multiclass classification problem of microarray data was proposed in this paper. You signed in with another tab or window. Multinomial Regression with Elastic Net Penalty and Its Grouping Effect in Gene Selection, School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China, School of Mathematics and Information Science, Henan Normal University, Xinxiang 453007, China, I. Guyon, J. Weston, S. Barnhill, and V. Vapnik, “Gene selection for cancer classification using support vector machines,”, R. Tibshirani, “Regression shrinkage and selection via the lasso,”, L. Wang, J. Zhu, and H. Zou, “Hybrid huberized support vector machines for microarray classification and gene selection,”, L. Wang, J. Zhu, and H. Zou, “The doubly regularized support vector machine,”, J. Zhu, R. Rosset, and T. Hastie, “1-norm support vector machine,” in, G. C. Cawley and N. L. C. Talbot, “Gene selection in cancer classification using sparse logistic regression with Bayesian regularization,”, H. Zou and T. Hastie, “Regularization and variable selection via the elastic net,”, J. Li, Y. Jia, and Z. Zhao, “Partly adaptive elastic net and its application to microarray classification,”, Y. Lee, Y. Lin, and G. Wahba, “Multicategory support vector machines: theory and application to the classification of microarray data and satellite radiance data,”, X. Zhou and D. P. Tuck, “MSVM-RFE: extensions of SVM-RFE for multiclass gene selection on DNA microarray data,”, S. Student and K. Fujarewicz, “Stable feature selection and classification algorithms for multiclass microarray data,”, H. H. Zhang, Y. Liu, Y. Wu, and J. Zhu, “Variable selection for the multicategory SVM via adaptive sup-norm regularization,”, J.-T. Li and Y.-M. Jia, “Huberized multiclass support vector machine for microarray classification,”, M. You and G.-Z. Specifically, we introduce sparsity … However, the aforementioned binary classification methods cannot be applied to the multiclass classification easily. In the multi class logistic regression python Logistic Regression class, multi-class classification can be enabled/disabled by passing values to the argument called ‘‘multi_class’ in the constructor of the algorithm. Equation (40) can be easily solved by using the R package “glmnet” which is publicly available. But like lasso and ridge, elastic net can also be used for classification by using the deviance instead of the residual sum of squares. where represent a pair of parameters which corresponds to the sample , and , . For the microarray data, and represent the number of experiments and the number of genes, respectively. For the multiclass classification problem of microarray data, a new optimization model named multinomial regression with the elastic net penalty was proposed in this paper. Analytics cookies. ElasticNet Regression – L1 + L2 regularization. Hence, from (24) and (25), we can get The Data. The authors declare that there is no conflict of interests regarding the publication of this paper. holds if and only if . Regularize binomial regression. It also includes sectionsdiscussing specific classes of algorithms, such as linear methods, trees, and ensembles. Multinomial Naive Bayes is designed for text classification. The logistic regression model represents the following class-conditional probabilities; that is, Let On the other hand, if $\alpha$ is set to $0$, the trained model reduces to a ridge regression model. Restricted by the high experiment cost, only a few (less than one hundred) samples can be obtained with thousands of genes in one sample. It should be noted that if . they're used to gather information about the pages you visit and how many clicks you need to accomplish a task. Copyright © 2014 Liuyuan Chen et al. Concepts. Multilayer perceptron classifier 1.6. It is ignored when solver = ‘liblinear’. Linear Support Vector Machine 1.7. This means that the multinomial regression with elastic net penalty can select genes in groups according to their correlation. This is equivalent to maximizing the likelihood of the data set under the model parameterized by . For convenience, we further let and represent the th row vector and th column vector of the parameter matrix . class sklearn.linear_model. Regularize a model with many more predictors than observations. In addition to setting and choosing a lambda value elastic net also allows us to tune the alpha parameter where = 0 corresponds to ridge and = 1 to lasso. We will use a real world Cancer dataset from a 1989 study to learn about other types of regression, shrinkage, and why sometimes linear regression is not sufficient. Recall in Chapter 1 and Chapter 7, the definition of odds was introduced – an odds is the ratio of the probability of some event will take place over the probability of the event will not take place. The loss function is strongly convex, and hence a unique minimum exists. I have discussed Logistic regression from scratch, deriving principal components from the singular value decomposition and genetic algorithms. In statistics and, in particular, in the fitting of linear or logistic regression models, the elastic net is a regularized regression method that linearly combines the L1 and L2 penalties of the lasso and ridge methods. Fit multiclass models for support vector machines or other classifiers: predict: Predict labels for linear classification models: ... Identify and remove redundant predictors from a generalized linear model. Regularize Wide Data in Parallel. Using caret package. It is basically the Elastic-Net mixing parameter with 0 < = l1_ratio > = 1. Note that the function is Lipschitz continuous. Lasso Regularization of … Without loss of generality, it is assumed that. coefficientMatrix)) print ("Intercept: "+ str (lrModel. Ask Question Asked 2 years, 6 months ago. 15: l1_ratio − float or None, optional, dgtefault = None. Decision tree classifier 1.3. If you would like to see an implementation with Scikit-Learn, read the previous article. By combing the multiclass elastic net penalty (18) with the multinomial likelihood loss function (17), we propose the following multinomial regression model with the elastic net penalty: One-vs-Rest classifier (a.k.a… Give the training data set and assume that the matrix and vector satisfy (1). ∙ 0 ∙ share Multi-task learning has shown to significantly enhance the performance of multiple related learning tasks in a variety of situations. Sign up here as a reviewer to help fast-track new submissions. According to the inequality shown in Theorem 2, the multinomial regression with elastic net penalty can assign the same parameter vectors (i.e., ) to the high correlated predictors (i.e., ). Note that ElasticNet(alpha=1.0, *, l1_ratio=0.5, fit_intercept=True, normalize=False, precompute=False, max_iter=1000, copy_X=True, tol=0.0001, warm_start=False, positive=False, random_state=None, selection='cyclic') [source] ¶. The elastic net method includes the LASSO and ridge regression: in other words, each of them is a special case where =, = or =, =. First of all, we construct the new parameter pairs , where The notion of odds will be used in how one represents the probability of the response in the regression model. Table of Contents 1. The inputs and outputs of multi-class logistic regression are similar to those of logistic regression. ElasticNet regression is a type of linear model that uses a combination of ridge and lasso regression as the shrinkage. Elastic Net is a method for modeling relationship between a dependent variable (which may be a vector) and one or more explanatory variables by fitting regularized least squares model. The emergence of the sparse multinomial regression provides a reasonable application to the multiclass classification of microarray data that featured with identifying important genes [20–22]. In the next work, we will apply this optimization model to the real microarray data and verify the specific biological significance. Let us first start by defining the likelihood and loss : While entire books are dedicated to the topic of minimization, gradient descent is by far the simplest method for minimizing arbitrary non-linear … According to the technical term in [14], this performance is called grouping effect in gene selection for multiclass classification. load ("data/mllib/sample_multiclass_classification_data.txt") lr = LogisticRegression (maxIter = 10, regParam = 0.3, elasticNetParam = 0.8) # Fit the model: lrModel = lr. Hence, inequality (21) holds. 2014, Article ID 569501, 7 pages, 2014. https://doi.org/10.1155/2014/569501, 1School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China, 2School of Mathematics and Information Science, Henan Normal University, Xinxiang 453007, China. To improve the solving speed, Friedman et al. The trained model can then be used to predict values f… Li, “Feature selection for multi-class problems by using pairwise-class and all-class techniques,”, M. Y. Support vector machine [1], lasso [2], and their expansions, such as the hybrid huberized support vector machine [3], the doubly regularized support vector machine [4], the 1-norm support vector machine [5], the sparse logistic regression [6], the elastic net [7], and the improved elastic net [8], have been successfully applied to the binary classification problems of microarray data. Theorem 2. 4. Classification using logistic regression is a supervised learning method, and therefore requires a labeled dataset. In the training phase, the inputs are features and labels of the samples in the training set, … Logistic Regression (with Elastic Net Regularization) ... Multi-class logistic regression (also referred to as multinomial logistic regression) extends binary logistic regression algorithm (two classes) to multi-class cases. From (33) and (21) and the definition of the parameter pairs , we have PySpark: Logistic Regression Elastic Net Regularization. In 2014, it was proven that the Elastic Net can be reduced to a linear support vector machine. This essentially happens automatically in caret if the response variable is a factor. Note that, we can easily compute and compare ridge, lasso and elastic net regression using the caret workflow. Elastic Net. also known as maximum entropy classifiers ? 12.4.2 A logistic regression model. PySpark's Logistic regression accepts an elasticNetParam parameter. To this end, we must first prove the inequality shown in Theorem 1. The elastic net method includes the LASSO and ridge regression: in other words, each of them is a special case where =, = or =, =. Kim, and S. Boyd, “An interior-point method for large-scale, C. Xu, Z. M. Peng, and W. F. Jing, “Sparse kernel logistic regression based on, Y. Yang, N. Kenneth, and S. Kim, “A novel k-mer mixture logistic regression for methylation susceptibility modeling of CpG dinucleotides in human gene promoters,”, G. C. Cawley, N. L. C. Talbot, and M. Girolami, “Sparse multinomial logistic regression via Bayesian L1 regularization,” in, N. Lama and M. Girolami, “vbmp: variational Bayesian multinomial probit regression for multi-class classification in R,”, J. Sreekumar, C. J. F. ter Braak, R. C. H. J. van Ham, and A. D. J. van Dijk, “Correlated mutations via regularized multinomial regression,”, J. Friedman, T. Hastie, and R. Tibshirani, “Regularization paths for generalized linear models via coordinate descent,”. For example, if a linear regression model is trained with the elastic net parameter $\alpha$ set to $1$, it is equivalent to a Lasso model. Elastic-Net Regression is combines Lasso Regression with Ridge Regression to give you the best of both worlds. . For elastic net regression, you need to choose a value of alpha somewhere between 0 and 1. Logistic regression 1.1.1. For the multiclass classi cation problem of microarray data, a new optimization model named multinomial regression with the elastic net penalty was proposed in this paper. The elastic net regression performs L1 + L2 regularization. From (37), it can be easily obtained that Regularize a model with many more predictors than observations. It is used in case when penalty = ‘elasticnet’. We present the fused logistic regression, a sparse multi-task learning approach for binary classification. Let and , where , . The multiclass classifier can be represented as It can be applied to the multiple sequence alignment of protein related to mutation. By solving an optimization formula, a new multicategory support vector machine was proposed in [9]. The goal of binary classification is to predict a value that can be one of just two discrete possibilities, for example, predicting if a … Similarly, we can construct the th as Let and If I set this parameter to let's say 0.2, what does it mean? Particularly, for the binary classification, that is, , inequality (29) becomes By using the elastic net penalty, the regularized multinomial regression model was developed in [22]. Multiclass classification with logistic regression can be done either through the one-vs-rest scheme in which for each class a binary classification problem of data belonging or not to that class is done, or changing the loss function to cross- entropy loss. The simplified format is as follow: glmnet(x, y, family = "binomial", alpha = 1, lambda = NULL) x: matrix of predictor variables. About multiclass logistic regression. section 4. Analogically, we have Logistic Regression (with Elastic Net Regularization) Logistic regression models the relationship between a dichotomous dependent variable (also known as explained variable) and one or more continuous or categorical independent variables (also known as explanatory variables). where . Above, we have performed a regression task. # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. In this paper, we pay attention to the multiclass classification problems, which imply that . ... Logistic Regression using TF-IDF Features. So, here we are now, using Spark Machine Learning Library to solve a multi-class text classification problem, in particular, PySpark. For validation, the developed approach is applied to experimental data acquired on a shaker blower system (as representative of aeronautical … Simply put, if you plug in 0 for alpha, the penalty function reduces to the L1 (ridge) term … We’ll use the R function glmnet () [glmnet package] for computing penalized logistic regression. This chapter described how to compute penalized logistic regression model in R. Here, we focused on lasso model, but you can also fit the ridge regression by using alpha = 0 in the glmnet() function. Then (13) can be rewritten as Multinomial regression can be obtained when applying the logistic regression to the multiclass classification problem. caret will automatically choose the best tuning parameter values, compute the final model and evaluate the model performance using cross-validation techniques. Then extending the class-conditional probabilities of the logistic regression model to -logits, we have the following formula: as for instance the objective induced by the fused elastic net logistic regression. If multi_class = ‘ovr’, this parameter represents the number of CPU cores used when parallelizing over classes. A Fused Elastic Net Logistic Regression Model for Multi-Task Binary Classification. We will be providing unlimited waivers of publication charges for accepted research articles as well as case reports and case series related to COVID-19. So the loss function changes to the following equation. Elastic Net regression model has the special penalty, a sum of 12/30/2013 ∙ by Venelin Mitov, et al. The proposed multinomial regression is proved to encourage a grouping effect in gene selection. Hence, If I set this parameter to let's say 0.2, what does it … If the pairs () are the optimal solution of the multinomial regression with elastic net penalty (19), then the following inequality # The ASF licenses this file to You under the Apache License, Version 2.0, # (the "License"); you may not use this file except in compliance with, # the License. that is, where represent the regularization parameter. We use analytics cookies to understand how you use our websites so we can make them better, e.g. where represents bias and represents the parameter vector. We are committed to sharing findings related to COVID-19 as quickly as possible. Review articles are excluded from this waiver policy. In the section, we will prove that the multinomial regression with elastic net penalty can encourage a grouping effect in gene selection. From (22), it can be easily obtained that For example, smoothing matrices penalize functions with large second derivatives, so that the regularization parameter allows you to "dial in" a regression which is a nice compromise between over- and under-fitting the data. Viewed 2k times 1. Random forest classifier 1.4. that is, Regression Accuracy Check in Python (MAE, MSE, RMSE, R-Squared) Regression Example with Keras LSTM Networks in R Classification Example with XGBClassifier in Python Hence, we have interceptVector)) This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The algorithm predicts the probability of occurrence of an event by fitting data to a logistic function. It's a lot faster than plain Naive Bayes. The Elastic Net is an extension of the Lasso, it combines both L1 and L2 regularization. Classification 1.1. Logistic Regression (aka logit, MaxEnt) classifier. Concepts. In the multiclass case, the training algorithm uses the one-vs-rest (OvR) scheme if the ‘multi_class’ option is set to ‘ovr’, and uses the cross-entropy loss if the ‘multi_class’ option is set to ‘multinomial’. Articles Related Documentation / Reference Elastic_net_regularization. This corresponds with the results in [7]. A third commonly used model of regression is the Elastic Net which incorporates penalties from both L1 and L2 regularization: Elastic net regularization. $\begingroup$ Ridge, lasso and elastic net regression are popular options, but they aren't the only regularization options. Because the number of the genes in microarray data is very large, it will result in the curse of dimensionality to solve the proposed multinomial regression. This completes the proof. Microsoft Research's Dr. James McCaffrey show how to perform binary classification with logistic regression using the Microsoft ML.NET code library. To this end, we convert (19) into the following form: This article describes how to use the Multiclass Logistic Regressionmodule in Azure Machine Learning Studio (classic), to create a logistic regression model that can be used to predict multiple values. Liuyuan Chen, Jie Yang, Juntao Li, Xiaoyu Wang, "Multinomial Regression with Elastic Net Penalty and Its Grouping Effect in Gene Selection", Abstract and Applied Analysis, vol. Multiclass logistic regression is also referred to as multinomial regression. Hence, the multiclass classification problems are the difficult issues in microarray classification [9–11]. You may obtain a copy of the License at, # http://www.apache.org/licenses/LICENSE-2.0, # Unless required by applicable law or agreed to in writing, software. Recall in Chapter 1 and Chapter 7, the definition of odds was introduced – an odds is the ratio of the probability of some event will take place over the probability of the event will not take place. Microarray is the typical small , large problem. Array must have length equal to the number of classes, with values > 0 excepting that at most one value may be 0. Note that . By combining the multinomial likeliyhood loss and the multiclass elastic net Regularize binomial regression. proposed the pairwise coordinate decent algorithm which takes advantage of the sparse property of characteristic. See the NOTICE file distributed with. ... For multiple-class classification problems, refer to Multi-Class Logistic Regression. Note that the inequality holds for the arbitrary real numbers and . holds, where , is the th column of parameter matrix , and is the th column of parameter matrix . The objective of this work is the development of a fault diagnostic system for a shaker blower used in on-board aeronautical systems. Regularize Logistic Regression. It can be easily obtained that Regularize Wide Data in Parallel. from pyspark.ml.feature import HashingTF, IDF hashingTF = HashingTF ... 0.2]) # Elastic Net Parameter … Cannot retrieve contributors at this time, # Licensed to the Apache Software Foundation (ASF) under one or more, # contributor license agreements. In this article, we will cover how Logistic Regression (LR) algorithm works and how to run logistic regression classifier in python. Proof. For the multiclass classification of the microarray data, this paper combined the multinomial likelihood loss function having explicit probability meanings [23] with multiclass elastic net penalty selecting genes in groups [14], proposed a multinomial regression with elastic net penalty, and proved that this model can encourage a grouping effect in gene selection at the same time of classification. For the binary classification problem, the class labels are assumed to belong to . Therefore, we choose the pairwise coordinate decent algorithm to solve the multinomial regression with elastic net penalty. The Elastic Net is … Logistic Regression (with Elastic Net Regularization) Logistic regression models the relationship between a dichotomous dependent variable (also known as explained variable) and one or more continuous or categorical independent variables (also known as explanatory variables). Lasso Regularization of … holds, where and represent the first rows of vectors and and and represent the first rows of matrices and . For any new parameter pairs which are selected as , the following inequality To automatically select genes during performing the multiclass classification, new optimization models [12–14], such as the norm multiclass support vector machine in [12], the multicategory support vector machine with sup norm regularization in [13], and the huberized multiclass support vector machine in [14], were developed. Elastic Net first emerged as a result of critique on lasso, whose variable selection can … Regularize Logistic Regression. However, this optimization model needs to select genes using the additional methods. Let . Regularize a model with many more predictors than observations. Multinomial logistic regression 1.2. Lasso Regularization of … You train the model by providing the model and the labeled dataset as an input to a module such as Train Model or Tune Model Hyperparameters. This work is supported by Natural Science Foundation of China (61203293, 61374079), Key Scientific and Technological Project of Henan Province (122102210131, 122102210132), Program for Science and Technology Innovation Talents in Universities of Henan Province (13HASTIT040), Foundation and Advanced Technology Research Program of Henan Province (132300410389, 132300410390, 122300410414, and 132300410432), Foundation of Henan Educational Committee (13A120524), and Henan Higher School Funding Scheme for Young Teachers (2012GGJS-063). It can be successfully used to microarray classification [9]. Let be the decision function, where . This page covers algorithms for Classification and Regression. # See the License for the specific language governing permissions and, "MulticlassLogisticRegressionWithElasticNet", "data/mllib/sample_multiclass_classification_data.txt", # Print the coefficients and intercept for multinomial logistic regression, # for multiclass, we can inspect metrics on a per-label basis. Features extracted from condition monitoring signals and selected by the ELastic NET (ELNET) algorithm, which combines l 1-penalty with the squared l 2-penalty on model parameters, are used as inputs of a Multinomial Logistic regression (MLR) model. Theorem 1. It is easily obtained that Regularize Wide Data in Parallel. It is one of the most widely used algorithm for classification… Park and T. Hastie, “Penalized logistic regression for detecting gene interactions,”, K. Koh, S.-J. Therefore, the class-conditional probabilities of multiclass classification problem can be represented as, Following the idea of sparse multinomial regression [20–22], we fit the above class-conditional probability model by the regularized multinomial likelihood. By combining the multinomial likeliyhood loss and the multiclass elastic net penalty, the optimization model was constructed, which was proved to encourage a grouping effect in gene selection for multiclass classification. y: the response or outcome variable, which is a binary variable. For the multiclass classification problem of microarray data, a new optimization model named multinomial regression with the elastic net penalty was proposed in this paper. Concepts. # this work for additional information regarding copyright ownership. By adopting a data augmentation strategy with Gaussian latent variables, the variational Bayesian multinomial probit model which can reduce the prediction error was presented in [21]. fit (training) # Print the coefficients and intercept for multinomial logistic regression: print ("Coefficients: \n " + str (lrModel. Regularize binomial regression. where Proof. family: the response type. Elastic Net. Although the above sparse multinomial models achieved good prediction results on the real data, all of them failed to select genes (or variables) in groups. Substituting (34) and (35) into (32) gives Active 2 years, 6 months ago. The notion of odds will be used in how one represents the probability of the response in the regression model. Considering a training data set … By using Bayesian regularization, the sparse multinomial regression model was proposed in [20]. In the case of multi-class logistic regression, it is very common to use the negative log-likelihood as the loss. Minimizes the objective function: The elastic net regression by default adds the L1 as well as L2 regularization penalty i.e it adds the absolute value of the magnitude of the coefficient and the square of the magnitude of the coefficient to the loss function respectively. Using the results in Theorem 1, we prove that the multinomial regression with elastic net penalty (19) can encourage a grouping effect. According to the common linear regression model, can be predicted as Let be the solution of the optimization problem (19) or (20). Hence, the multinomial likelihood loss function can be defined as, In order to improve the performance of gene selection, the following elastic net penalty for the multiclass classification problem was proposed in [14] Gradient-boosted tree classifier 1.5. Regularize Logistic Regression. 12.4.2 A logistic regression model. Binomial logistic regression 1.1.2. Logistic regression is a well-known method in statistics that is used to predict the probability of an outcome, and is popular for classification tasks. The Alternating Direction Method of Multipliers (ADMM) [2] is an opti- Features extracted from condition monitoring signals and selected by the ELastic NET (ELNET) algorithm, which combines l 1-penalty with the squared l 2-penalty on model parameters, are used as inputs of a Multinomial Logistic regression (MLR) model. Shrinkage in the sense it reduces the coefficients of the model thereby simplifying the model. Since the pairs () are the optimal solution of the multinomial regression with elastic net penalty (19), it can be easily obtained that Note that Let and then Fit multiclass models for support vector machines or other classifiers: predict: Predict labels for linear classification models: ... Identify and remove redundant predictors from a generalized linear model. Note that the logistic loss function not only has good statistical significance but also is second order differentiable.