1. STATEMENT USED TO CREATE RANDOM POINTS IN STUDY AREA GRID, WHERE STUDY AREA GRID HAS VALUES = 1 FOR AREAS WITHIN STUDY AREA, ELSE NODATA:
IN GRID: outfile = con(infile eq 1, con(rand (.) < 0.00077, 1)
Where 0.00077 is the proportion of the total number of cells in the grid that are desired as random points.
2. FORMULA FOR CORRECTED Y-INTERCEPT, USED BECAUSE WE HAD A DIFFERENT NUMBER OF RANDOM POINTS (0 IN THE LOGISTIC REGRESSION) AND COYOTE LOCATIONS (1 IN THE LOGISTIC REGRESSION):
a’ = a + ln (n2/n1)
Where a is the Y-intercept in the regression, a’ is the corrected Y-intercept, ln is a natural logarithm, n1 is the number of cases in the smaller sample, and n2 is the number of cases in the larger sample. This equation follows Warren , R. E. 1990.
3. FORMULA FOR LOGISTIC TRANSFORMATION OF PROBABILITY GRID:
IN GRID: docell
temp1:= exp (-in_grid)
outgrid = 1/(1 + temp1)
end