I have formatted my dataset to create variables of fire spread direction (angle between the centroid of the burned area and start of fire) and wind direction (angle the wind is blowing towards).
So far, I have considered: converting these angles to discrete categorical variables (0: North, 1: Northeast ... 7: Northwest), and then running a logit on the variable octant_angle_diff (e.g. +1 if fire_angle is East and wind_angle is South-east). I'm not sure how to interpret the estimate, though I think it would be a measure of how wind direction (as the deviation of wind angle from fire spread angle) is a predictor of fire spread direction.
Example:
Code:
clear all input fire_id fire_angle wind_angle angle_diff 1 32 45 13 2 266 225 -41 3 104 270 166 4 220 45 -175 5 82 0 -82 6 45 45 0 7 85 225 140 8 80 270 -170 9 262 270 8 10 253 225 -28 end gen fire_angle_octant = 0 if (fire_angle > (15 * 22.5) | fire_angle <= (1 * 22.5)) replace fire_angle_octant = 1 if (fire_angle > (1 * 22.5) & fire_angle <= (3 * 22.5)) replace fire_angle_octant = 2 if (fire_angle > (3 * 22.5) & fire_angle <= (5 * 22.5)) replace fire_angle_octant = 3 if (fire_angle > (5 * 22.5) & fire_angle <= (7 * 22.5)) replace fire_angle_octant = 4 if (fire_angle > (7 * 22.5) & fire_angle <= (9 * 22.5)) replace fire_angle_octant = 5 if (fire_angle > (9 * 22.5) & fire_angle <= (11 * 22.5)) replace fire_angle_octant = 6 if (fire_angle > (11 * 22.5) & fire_angle <= (13 * 22.5)) replace fire_angle_octant = 7 if (fire_angle > (13 * 22.5) & fire_angle <= (15 * 22.5)) gen wind_angle_octant = 0 if (wind_angle > (15 * 22.5) | wind_angle <= (1 * 22.5)) replace wind_angle_octant = 1 if (wind_angle > (1 * 22.5) & wind_angle <= (3 * 22.5)) replace wind_angle_octant = 2 if (wind_angle > (3 * 22.5) & wind_angle <= (5 * 22.5)) replace wind_angle_octant = 3 if (wind_angle > (5 * 22.5) & wind_angle <= (7 * 22.5)) replace wind_angle_octant = 4 if (wind_angle > (7 * 22.5) & wind_angle <= (9 * 22.5)) replace wind_angle_octant = 5 if (wind_angle > (9 * 22.5) & wind_angle <= (11 * 22.5)) replace wind_angle_octant = 6 if (wind_angle > (11 * 22.5) & wind_angle <= (13 * 22.5)) replace wind_angle_octant = 7 if (wind_angle > (13 * 22.5) & wind_angle <= (15 * 22.5)) gen octant_angle_diff = wind_angle_octant - fire_angle_octant mlogit octant_angle_diff
Michael
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