Linear, Deterministic, and Order-Invariant Initialization Methods for the K-Means Clustering Algorithm

Over the past five decades, k-means has become the clustering algorithm of choice in many application domains primarily due to its simplicity, time/space efficiency, and invariance to the ordering of the data points. Unfortunately, the algorithm's sensitivity to the initial selection of the cluster centers remains to be its most serious drawback. Numerous initialization methods have been proposed to address this drawback. Many of these methods, however, have time complexity superlinear in the number of data points, which makes them impractical for large data sets. On the other hand, linear methods are often random and/or sensitive to the ordering of the data points. These methods are generally unreliable in that the quality of their results is unpredictable. Therefore, it is common practice to perform multiple runs of such methods and take the output of the run that produces the best results. Such a practice, however, greatly increases the computational requirements of the otherwise highly efficient k-means algorithm. In this chapter, we investigate the empirical performance of six linear, deterministic (non-random), and order-invariant k-means initialization methods on a large and diverse collection of data sets from the UCI Machine Learning Repository. The results demonstrate that two relatively unknown hierarchical initialization methods due to Su and Dy outperform the remaining four methods with respect to two objective effectiveness criteria. In addition, a recent method due to Erisoglu et al. performs surprisingly poorly.Comment: 21 pages, 2 figures, 5 tables, Partitional Clustering Algorithms (Springer, 2014). arXiv admin note: substantial text overlap with arXiv:1304.7465, arXiv:1209.196

State owned enterprises as bribe payers: the role of institutional environment

Our paper draws attention to a neglected channel of corruption—the bribe payments by state-owned enterprises (SOEs). This is an important phenomenon as bribe payments by SOEs fruitlessly waste national resources, compromising public welfare and national prosperity. Using a large dataset of 30,249 firms from 50 countries, we show that, in general, SOEs are less likely to pay bribes for achieving organizational objectives owing to their political connectivity. However, in deteriorated institutional environments, SOEs may be subjected to potential managerial rent-seeking behaviors, which disproportionately increase SOE bribe propensity relative to privately owned enterprises. Specifically, our findings highlight the importance of fostering democracy and rule of law, reducing prevalence of corruption and shortening power distance in reducing the incidence of SOE bribery

Clinical guidelines for the recognition of melanoma of the foot and nail unit

Malignant melanoma is a life threatening skin tumour which may arise on the foot. The prognosis for the condition is good when lesions are diagnosed and treated early. However, lesions arising on the soles and within the nail unit can be difficult to recognise leading to delays in diagnosis. These guidelines have been drafted to alert health care practitioners to the early signs of the disease so an early diagnosis can be sought<br/

Italian Identity in the United States

none1siItaly’s belated completion of political unification in 1861 let the Italian people long retain a regional, provincial, and even local identity. Likewise, the newcomers who arrived in the United States from different places in Italy between the late 1870s and the closing of mass immigration in the mid-1920s found it difficult to perceive themselves as members of the same ethnic minority and shied away from one another not only in areas of residence but also in social and religious life at the beginning of their stay in America. By the late 1930s, however, the emergence and consolidation of nationalistic feelings, following both Italy’s entry into World War I and Fascist aggressive foreign policy, immigration restriction, the appearance of a US-born second generation with loose ties to the forebears’ land, and, primarily, the experience of anti-Italian intolerance and discrimination in the United States made people of Italian descent aware of their common national ancestry and helped them develope an Italian identity that they or their parents had lacked upon settling in the United States. Racial tensions and the backlash at blacks’ supposed encroachments in the postwar decades encouraged many Italian Americans to join forces with other immigrant groups of European origin from which they had previously distanced themselves. They, therefore, acquired a racial sense of belonging as white Europeans and nowadays retain an Italian identity only at a symbolic level, almost exclusively in leisure time activities.embargoed_20220710LUCONI, StefanoLuconi, Stefan