file 3: "3_spatial_density_distribution_predation.csv"

The data in the different columns represent:
sampling_station	-	id of sampling station
plot				-	factor indicating which plot the data were collected; ("A", "B", or "I")
predation			-	factor indicating predation "treatment"; "yes" indicates a predation plot, and "no" indicates the reference plot 
sampling_occassion	-	factor indicating the sampling occasion; "before" indicates initial sampling, and "post_pred" indicates final sampling 
X_m					-	the X-coordinate of the sampling station in meters
Y_m					-	the Y-coordinate of the sampling station in meters
cockles_n			-	the number of cockles < 16 mm in the sampling core