Logistic regression is a widely used method in several fields. When applying logistic regression to imbalanced data, for which majority classes dominate over minority classes, all class labels are estimated as `majority class.' In this article, we use an F-measure optimization method to improve the performance of logistic regression applied to imbalanced data. While many F-measure optimization methods adopt a ratio of the estimators to approximate the F-measure, the ratio of the estimators tends to have more bias than when the ratio is directly approximated. Therefore, we employ an approximate F-measure for estimating the relative density ratio. In addition, we define a relative F-measure and approximate the relative F-measure. We show an algorithm for a logistic regression weighted approximated relative to the F-measure. The experimental results using real world data demonstrated that our proposed method is an efficient algorithm to improve the performance of logistic regression applied to imbalanced data.

Efficient explorative data analysis systems must take into account both what a user knows and wants to know. This paper proposes a principled framework for interactive visual exploration of relations in data, through views most informative given the user's current knowledge and objectives. The user can input pre-existing knowledge of relations in the data and also formulate specific exploration interests, then taken into account in the exploration. The idea is to steer the exploration process towards the interests of the user, instead of showing uninteresting or already known relations. The user's knowledge is modelled by a distribution over data sets parametrised by subsets of rows and columns of data, called tile constraints. We provide a computationally efficient implementation of this concept based on constrained randomisation. Furthermore, we describe a novel dimensionality reduction method for finding the views most informative to the user, which at the limit of no background knowledge and with generic objectives reduces to PCA. We show that the method is suitable for interactive use and robust to noise, outperforms standard projection pursuit visualisation methods, and gives understandable and useful results in analysis of real-world data. We have released an open-source implementation of the framework.

While the finite-sum setting is a particular case of expectation, the deterministic nature of the resulting cost function In this paper, we propose a unified view of drastically changes the performance guarantees an optimization gradient-based algorithms for stochastic convex method may achieve to solve (1). In particular, when an composite optimization by extending the concept algorithm is only allowed to access unbiased measurements of estimate sequence introduced by Nesterov. of the objective and gradient, it may be shown that the worstcase This point of view covers the stochastic gradient convergence rate in expected function value cannot be descent method, variants of the approaches better than O(1/k) in general, where k is the number of SAGA, SVRG, and has several advantages: (i) iterations (Nemirovski et al., 2009; Agarwal et al., 2012).

Bayesian optimization is an effective method to efficiently optimize unknown objective functions with high evaluation costs. Traditional Bayesian optimization algorithms select one point per iteration for single objective function, whereas in recent years, Bayesian optimization for multi-objective optimization or multi-point search per iteration have been proposed. However, Bayesian optimization that can deal with them at the same time in non-heuristic way is not known at present. We propose a Bayesian optimization algorithm that can deal with multi-objective optimization and multi-point search at the same time. First, we define an acquisition function that considers both multi-objective and multi-point search problems. It is difficult to analytically maximize the acquisition function as the computational cost is prohibitive even when approximate calculations such as sampling approximation are performed; therefore, we propose an accurate and computationally efficient method for estimating gradient of the acquisition function, and develop an algorithm for Bayesian optimization with multi-objective and multi-point search. It is shown via numerical experiments that the performance of the proposed method is comparable or superior to those of heuristic methods.

Semi-supervised learning is sought for leveraging the unlabelled data when labelled data is difficult or expensive to acquire. Deep generative models (e.g., Variational Autoencoder (VAE)) and semisupervised Generative Adversarial Networks (GANs) have recently shown promising performance in semi-supervised classification for the excellent discriminative representing ability. However, the latent code learned by the traditional VAE is not exclusive (repeatable) for a specific input sample, which prevents it from excellent classification performance. In particular, the learned latent representation depends on a non-exclusive component which is stochastically sampled from the prior distribution. Moreover, the semi-supervised GAN models generate data from pre-defined distribution (e.g., Gaussian noises) which is independent of the input data distribution and may obstruct the convergence and is difficult to control the distribution of the generated data. To address the aforementioned issues, we propose a novel Adversarial Variational Embedding (AVAE) framework for robust and effective semi-supervised learning to leverage both the advantage of GAN as a high quality generative model and VAE as a posterior distribution learner. The proposed approach first produces an exclusive latent code by the model which we call VAE++, and meanwhile, provides a meaningful prior distribution for the generator of GAN. The proposed approach is evaluated over four different real-world applications and we show that our method outperforms the state-of-the-art models, which confirms that the combination of VAE++ and GAN can provide significant improvements in semisupervised classification.

The paper presents a novel approach of spoofing wireless signals by using a general adversarial network (GAN) to generate and transmit synthetic signals that cannot be reliably distinguished from intended signals. It is of paramount importance to authenticate wireless signals at the PHY layer before they proceed through the receiver chain. For that purpose, various waveform, channel, and radio hardware features that are inherent to original wireless signals need to be captured. In the meantime, adversaries become sophisticated with the cognitive radio capability to record, analyze, and manipulate signals before spoofing. Building upon deep learning techniques, this paper introduces a spoofing attack by an adversary pair of a transmitter and a receiver that assume the generator and discriminator roles in the GAN and play a minimax game to generate the best spoofing signals that aim to fool the best trained defense mechanism. The output of this approach is two-fold. From the attacker point of view, a deep learning-based spoofing mechanism is trained to potentially fool a defense mechanism such as RF fingerprinting. From the defender point of view, a deep learning-based defense mechanism is trained against potential spoofing attacks when an adversary pair of a transmitter and a receiver cooperates. The probability that the spoofing signal is misclassified as the intended signal is measured for random signal, replay, and GAN-based spoofing attacks. Results show that the GAN-based spoofing attack provides a major increase in the success probability of wireless signal spoofing even when a deep learning classifier is used as the defense.

We are destroying nature at an unprecedented rate, threatening the survival of a million species – and our own future, too. But it's not too late to save them and us, says a major new report. Our destruction of biodiversity and ecosystem services has reached levels that threaten our well-being at least as much as human-induced climate change." With these words chair Robert Watson launched a meeting in Paris to agree the final text of a major UN report on the state of nature around the world – the biggest and most thorough assessment to date, put together by 150 scientists from 50 countries. The report, released today, is mostly grim reading.

The BBC is developing a voice-activated electronic assistant in an attempt to rival Amazon's Alexa or Apple's Siri. It will similarly be styled as a character – currently dubbed'Auntie' by insiders in a nod to the BBC's longstanding nickname – but will be renamed before launch to make it more'modern-sounding'. The assistant would be available to download free on smartphones and smart TVs in the UK. It would allow users to seek information across the internet by issuing a verbal instruction. The BBC is developing a voice-activated electronic assistant in an attempt to rival Amazon's Alexa (pictured) For example, users could ask the app to get weather reports, play the most recent episode of The Archers or work out the quickest route to work.

Apple will be the subject of an anti-competition investigation by the European Union according to a report by the Financial Times. The investigation will focus on allegations by music-streaming platform, Spotify, who filed a complaint with the EU in March. According to the company, Apple -- which offers its own music streaming service called Apple Music -- has unfairly used the popularity of its platform to put Spotify and other companies like it at a disadvantage. This includes it's operating system, iOS, and the App Store. Spotify says Apple puts companies at a disadvantage by leveraging its App Store and iOS to lock companies out and charge them lofty fees.

CAPE CANAVERAL, FLORIDA - A SpaceX shipment arrived at the International Space Station on Monday with a "cosmic catch" by a pair of Canadians. The Dragon capsule delivered 5,500 pounds (2,500 kg) of equipment and experiments. Canadian astronaut David Saint-Jacques used the station's big robot arm -- also made in Canada -- to capture the Dragon approximately 250 miles (400 kilometers) above the North Atlantic Ocean. An external cable that normally comes off during launch dangled from the capsule, but it did not interfere with the grappling. "Welcome on board, Dragon," Saint-Jacques radioed. He congratulated ground teams for their help, in both English and French.