Simple Scan Tests for Spatial Clustering on a Square Lattice

Many data sets collected for study areas consist of data values collected on a square lattice or for a set of pixels. Remotely sensed data provide perhaps the most common example. Frequently, we wish to know whether there are subregions of the study area that exhibit spatial clustering. In this article, we suggest how an approach for finding spatial clusters may be combined with the common practice of using 3‐by‐3 and 5‐by‐5 smoothing filters or kernels to construct two simple and easy‐to‐implement scan‐type tests. A simulation experiment shows that the power of these tests to find clusters compares favorably with an alternative test that is more complicated. The tests use simulated data, changes in a remotely sensed image for a study region in Texas, and data about wheat yields. Muchas bases de datos que se recopilan para una zona de estudio, consisten en valores recopilados en una retícula cuadrada o en un conjunto de pixeles. Los datos obtenidos por sensores remotos son quizá el ejemplo más común. Frecuentemente deseamos saber si existen subregiones de la zona de estudio que exhiban agrupamiento espacial. En este artículo, sugerimos cómo una aproximación para ubicar agrupamientos espaciales se puede combinar con la práctica común de usar filtros de suavizado (kernels) de 3‐por‐3 y 5‐por‐5 filtros, para construir dos test tipo scan, sencillos y fáciles de implementar. Un experimento de simulación demuestra que el poder de estas pruebas para ubicar agrupamientos, se compara favorablemente frente a otra prueba alternativa, que resulta más complicada. Las pruebas usan datos simulados, cambios en una imagen de satélite para un área de estudio en Texas, y con data acerca de los rendimientos de cultivos de trigo. 研究区收集的许多数据集是由基于方格网和像素采集的数据值组成的,遥感数据可能提供了最常见的范例。通常,我们希望了解研究区的子区域是否呈现空间集聚特征。本文提出了一种如何发现空间集聚的方法,可以与采用3*3和5*5平滑滤波或核函数的普通试验相结合,构造两个简单且易于操作的扫描试验。模拟实验结果显示,这些试验在寻找聚集特征的性能上优于更复杂的可替换性试验。文中所用的仿真模拟数据来源于德克萨斯州小麦产量的多时相遥感影像。     

Documentary Evidence and the Medieval Pottery Industry

EARLY in my study of the medieval pottery industry it became clear to me that, contrary to general belief, a reasonable body of documentary evidence bearing on the industry had survived, but that it would take some years to assemble and interpret. There is no corpus of documents from which to begin, for surviving evidence is not only scattered in a very wide variety of documents, but is also dispersed geographically in a number of local record repositories. It might seem sensible to delay publication until a larger proportion of this evidence has been studied, or at least to avoid analysis and generalization at this stage; but pottery and potters are of interest to archaeologists here and now, and there is nothing written on the industry save assemblages of unrelated facts, often strung together from widely different periods. An effort has, therefore, been made to assemble the material so far available into a coherent pattern. Since this is the first time that this has been done, the result will probably require drastic modification in a few years' time. If the interim report here presented stimulates others to prove it wrong, this paper will have achieved at least one of its purposes.¹     

Contentious Realities: Politics of Creating an Image Archive with the Negev Bedouin in Southern Israel

This paper discusses the politics of creating an image archive amidst local Bedouin historicity in Southern Israel. To do so, it summarizes an archival initiative conducted during my fieldwork in Rāha?, Israel between 2011 and 2013, which broadly examined the presence and values of images in their society. I suggest that members compete over historical resources in attempts to augment limited cultural capital in the Negev, making efforts to collect and exhibit ‘shared’ histories contentious. This is particularly the case when local societies consider archival images rare artefacts and thus objects to be owned and protected. This paper concludes that control over archives and image objects, and the past, present, and future ideals to which they are used, is far from uniform amongst peripheral peoples in the Middle East. Visual evidence and the histories and presents it serves are indelibly localized within the prevailing status negotiations and current spatial divisions between Bedouin members in the Negev.     

State Making and the Politics of the Frontier in Central Benin

Kopytoff's model of the African frontier has opened room for renewed approaches to settlement history, politics, ethnicity and cultural reproduction in pre‐colonial Africa. This interpretative framework applies well to central Benin (Ouessè). Over the long term, mobility has been a structural feature of the regional social history, from pre‐colonial times onwards. Movements of people, resources, norms and values have been crucial in the production and reproduction of the social and political order. The colonial intrusion and its post‐colonial avatars gave way to renewed relations between mobility and locality, in particular in the form of a complex articulation between control over labour force, access to land and natural resources, and out‐ and in‐migrations. This article argues that the political frontier metaphor provides a useful heuristic device to capture the logic of state making, as the changing outcome of organizing practices taking place inside and outside state and non‐state organizations and arenas. Governmentality in post‐colonial central Benin thus results from the complex interplay of mobility, control over resources and state‐led forms of ‘villagization’.     

Book reviews

Economies of Signs & Space. Scott Lash and John Urry, London, Sage Publications, 1994, IV + 360 pp, £45.00 hb, ISBN 0 8039 8471 5; £13.95 pb, ISBN 0 8039 8472 3

Housing Policy in Action: The New Financial Regime for Council Housing. Peter Malpass, Matthew Warburton, Glen Bramley and Gavin Smart, SAUS Study 8, School for Advanced Urban Studies, University of Bristol, 1993, pp. XV+ 115, £9.75, ISBN 1 873575 47 5

Glasgow: The Forming of a City. Peter Reed (Ed.), Edinburgh, Edinburgh University Press, V+ 233 pp., £25.00, ISBN 0 7486 0246 1

Urban Land and Property Markets in Germany, European Land and Property Markets 2. H. Dietrich, E. Dransfeld and W. Voss, London, UCL Press, 288 pp, £40.00, ISBN 1 85728 049 0

The Politics of Local Economic Policy: Problems and Possibilities of Local Initiative. Aram Eisenschitz and Jamie Gough, London, Macmillan 1993, XIV + 309 pp, £14.99 pb, ISBN 0 33352 175 7

Planning at the Crossroads. James Simmie, London: UCL Press, 1993, 208 pp, £35.00, ISBN 1 85728 024 5, hb; 1 85728 025 3, pb; £12.95

The Political Culture of Planning: American Land Use Planning in a Comparative Perspective. J. Barry Cullingworth, New York and London, Routledge, 1993, XVII – 350 pp, £45.00, ISBN 0 415 08812 7, hb     

试析萧梁官班制度下的诸县分等

分析萧梁一代县官选任和调动案例可知,“县制七班”“大县六班”是当时客观存在的制度。但在制度的实际运行过程中,许多县官都会出现超班用人,即任职者官资超过县官对应内职班次的现象。正史所见高班大县全部位于扬、南徐二州境内,且主要隶属南朝国家腹心地区的丹阳、吴、吴兴、会稽等郡,这与史书记事的偏向性不无关系,但同时也是上述地区政治地理条件的直观反映。影响县官班次的最主要因素是人口,结合其他制度推测,等第最高的六班大县有可能是以领民满五千户为定等标准。探索县官班次,也可增进对当时人口地理的认知。