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gii = number of like adjacencies (joins) between pixels of patch type (class) i based on the double-count method. gik = number of adjacencies (joins) between pixels of patch types (classes) i and k based on the double-count method. |
| Description | PLADJ equals sum of the number of like adjacencies for each patch type, divided by the total number of cell adjacencies in the landscape; multiplied by 100 (to convert to a percentage). In other words, the proportion of cell adjacencies involving the same class. PLADJ considers all patch types present on an image, including any present in the landscape border, if present. All background edge segments are included in the denominator, including landscape boundary segments if a border is not provided. Cell adjacencies are tallied using the double-count method in which pixel order is preserved, at least for all internal adjacencies (i.e., involving cells on the inside of the landscape). If a landscape border is present, adjacencies on the landscape boundary are counted only once, as are all adjacencies with background. |
| Units | Percent |
| Range | 0 ≦ PLADJ ≦ 100 PLADJ equals 0 when the patch types are maximally disaggregated (i.e., every cell is a different patch type) and there are no like adjacencies. PLADJ = 100 when all patch types are maximally aggregated ( i.e., when the landscape consists of single patch and all adjacencies are between the same class), and the landscape contains a border comprised entirely of the same class. If the landscape consists of single patch but does not contain a border, PLADJ will be less than 100 due to the background edge segments along the boundary included in the tally of all adjacencies. PLADJ is undefined and reported as "N/A" in the "basename".land file if the landscape consists of a single non-background cell. |
| Comments | Percentage of like adjacencies is calculated from the adjacency matrix, which shows the frequency with which different pairs of patch types (including like adjacencies between the same patch type) appear side-by-side on the map. PLADJ measures the degree of aggregation of patch types. Thus, a landscape containing larger patches with simple shapes will contain a higher percentage of like adjacencies than a landscape with smaller patches and more complex shapes. In contrast to the contagion index at the landscape level, this metric measures only dispersion and not interspersion. Note, regardless of how much of the landscape is comprised of each class, this index will be minimum if all patch types are maximally dispersed (or disaggregated), and it will be maximum if all patch types are maximally contagious. |
