A modified Ripley´s K function to detecting spatial pattern of urban system

This paper uses a modified Ripley´s K function to examine the spatial evolution of urban system in the Yangtze River Delta (YRD) of China during the period of 1980-2010. Furthremore, we examine whether coastlines and provincial borders benefit the concentration of city location or size distribution in this region. The results show that: (1) the spatial evolution of the YRD city location distribution reflects the orientation of national urbanization strategy, while its urban size distribution evolves as a result of game between government and market. The pattern of urban system continuously shifts between concentration and dispersion. (2) Border effect on urban system´s distribution pattern is complex. Coastlines have positive effects on the agglomeration of the large cities with 0.5 to 1 million people, and provincial borders have positively or negatively influences on the YRD location and size. (3) The spillover effect of cities outside the YRD positively promotes the concentration of city location in terms of mega-cities, large-cities and small-cities. The size distribution of all cities, except for maga-cities, in the YRD shifts from concentration to dispersion.