These python codes are to calculate accessibility and access ratios based on the E2SFCA, M2SFCA, and 3SFCA methods. It could be seen as the very simple version of PySal. https://access.readthedocs.io/ However, I did not succeed in installing the package. Rather, I found it is quite simple to calculate accessibility if you have the distance matrix between census tracts and facilities. What is the meaning of "Accessibility" here? Here, accessibility means accessibility to public facilities. It is used to detect the distribution of public facilities, such as primary schools, hospitals, or even job opportunities. Using this indicator, we could identify which districts/areas in cities/regions has an inferior provision of the certain resource. What are E2SFCA, M2SFCA, and 3SFCA method? FCA: floating catchment area method. FCA methods calculate accessibility of one population unit (such as a community, census block, or census tract) as the sum of supply-demand ratios of the facilities are nearby to the unit. The facilities are in the catchment (buffer zone) of the population unit, and the population unit is within the catchment of the facilities too. See detailed instructions: http://geodacenter.github.io/docs/PySALAccess%20Package_Documentation.pdf 2SFCA: the two-step floating catchment area method. Luo, W., & Wang, F. (2003). Measures of spatial accessibility to health care in a GIS environment: synthesis and a case study in the Chicago Region. Environment and Planning B: Planning and Design, 30(6), 865-884. https://doi.org/10.1068/b29120 E2SFCA: the enhanced two-step floating catchment area method. Luo, W., & Qi, Y. (2009). An enhanced two-step floating catchment area (E2SFCA) method for measuring spatial accessibility to primary care physicians. Health & Place, 15(4), 1100-1107. https://doi.org/10.1016/j.healthplace.2009.06.002 M2SFCA: the modified two-step floating catchment area method. Delamater, P. L. (2013). Spatial accessibility in suboptimally configured health care systems: a modified two-step floating catchment area (M2SFCA) metric. Health & Place, 24, 30-43. https://doi.org/10.1016/j.healthplace.2013.07.012 3SFCA: the three-step floating catchment area method. Wan, N., Zou, B., & Sternberg, T. (2012). A three-step floating catchment area method for analyzing spatial access to health services. International Journal of Geographical Information Science, 26(6), 1073-1089. https://doi.org/10.1080/13658816.2011.624987 What is access ratios? Access ratios = distance weights * Accessibility (for each pair of facility and census tract). According to Wan, Zhan, et al. (2012), access ratios can reduce the high sensitivity of the distance decay coefficient on accessibility results and can produce relatively stable accessibility results. However, there might be some limitations in certain conditions. Wan, N., Zhan, F. B., Zou, B., & Chow, E. (2012). A relative spatial access assessment approach for analyzing potential spatial access to colorectal cancer services in Texas. Applied Geography, 32(2), 291-299. https://doi.org/10.1016/j.apgeog.2011.05.001

Three origin CSV files are required. 1. The population CSV in grid form (census blocks can work, but not recommended because of MAUP). With Unique Grid ID and population (as the demand for the facility, it can change into the number of pupils while measuring the accessibility to primary schools) # 2. The facility CSV. With Unique Facility ID and the service capacity. For example, the service capacity of one hospital can be the number of beds/physicians. 3. The distance matrix between each population grid and each facility. The matrix can be generated in the QGIS using the QNEAT3- distance matrix tool. It can generate a Euclidean distance matrix, network distance matrix, and travel time matrix. # Openstreetmap: Road Network, Facility Points # Population: WorldPop, Global High Resolution Population Denominators Project.2018 China population: https://dx.doi.org/10.5258/SOTON/WP00649 . This example is to calculate the accessibility to primary schools.

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