Descriptive Spatial Stats Pt. 2

Question 1

Mean direction

Answer 1

average direction of a set of data

Question 2

Median center

Answer 2

minimizes euclidean distance to all points

Question 3

Nearest neighbor analysis

Answer 3

calculate the nearest neighbor for each point and average

divide observed values/expected values

Question 4

Nearest neighbor analysis values

Answer 4

1 = random distribution
>1 dispersed
<1 clustered

Question 5

Quadrat analysis

Answer 5

establish a consistent grid and count # of points in each cell

calculate average in each cell

average this:|average - observed| for each cell

average variance / mean of points

Question 6

Quadrat analysis values

Answer 6

1 = random
>1 clustered
<1 dispersed

Question 7

Random pattern

Answer 7

exhibits no pattern

Question 8

Range

Answer 8

largest - smallest value

Question 9

Ripley’s K function

Answer 9

looking at clustering/dispersion at multiple distances

compares probability of detecting a difference in clustering compared to a specific probability (p) threshold

Question 10

Ripley’s k graph

Answer 10

if values are above the expected line then clustered

below line = dispersed

in confidence envelope = not significant clustering (random)

Question 11

standard deviational ellipse

Answer 11

shows direction/distance of distribution

calculates std dev of x and y coordinates from the mean center to define axes of ellipse

Question 12

standard distance

Answer 12

standard deviation applied to point data

measures dispersion of points and how far they are from the mean center

Question 13

weighted standard distance

Answer 13

takes into account locations in space/weights

measure of dispersion