ANLY482 AY2017-18 T2 Group 31 Model Buidling and Analysis
Model Building
Modified L Test via Ripley's K Function
To determine:
1. If the notifications appear to be clustered or randomly distributed in our area of interest
2. Minimum radius distance which shows signs of statistically significant clustering
Number of observed notifications is compared to the number of notifications expected based on Complete Spatial Randomness (CSR)
CSR assumes distribution of points is homogeneous over the study area
Null hypothesis: the spatial points are randomly distributed, using alpha = 0.01
Bold line represents the observed values for a range of π
Red dotted line represents the expected theoretical value for a range of π
Grey area is the confidence envelope obtained through 100 iterations of Monte Carlo procedures based on assumptions from CSR
For each simulated point pattern, πΎ(π) is estimated over a range of π. The max and min of these functions define an upper and lower simulation of the envelope
Converting K-function to L function, and to Modified L function
Interpreting the Modified L Test graph
Kernel Density Estimation
To determine:
1. To identify cluster of locations that have higher occurrence of indiscriminate parkings
Function (kernel π) of a given radius (π) βvisitsβ each point in the study region. π provides the weight of the area surrounding π in proportion to its distance to π _π
π is calculated as a function of the distance between point π and π _π, over given radius π
The density of the study region is obtained by summing π of all points π _π within π
Kernel Density Estimations are sensitive to changes in radius values
Large radius leads to a smoother curve, but local details would be obscured
Small radius leads to many small spikes that are very localised
Using the statistically significant radius distance obtained from Modified L Test as a search radius within each event
Perform interpolation by transforming the graph to make it smoother
Individual kernels are summed up to produce a smooth surface
Quartic kernel type is used in QGIS
