Random Number Generation - Infection - matlab

Question

InfectionMatrix = zeros(100,100);
InfectionMatrix(50,50) = 1;
for k = 1:1:90
[i,j] = find(InfectionMatrix > 0.7);
%Random Number Generator
a = 0.0270;
b = 0.3250;
RANDOM = (b-a).*rand(8,1) + a;
%%%%%%%%%%%%%%%%%%%%%%%%
i(i == 1) = [];
i(i == length(InfectionMatrix)) = [];
j(j == 1) = [];
j(j == length(InfectionMatrix)) = [];
InfectionMatrix(i-1,j) = InfectionMatrix(i-1,j)+ RANDOM(1);
InfectionMatrix(i-1,j+1) = InfectionMatrix(i-1,j+1)+ RANDOM(2);
InfectionMatrix(i-1,j-1) = InfectionMatrix(i-1,j-1)+ RANDOM(3);
InfectionMatrix(i,j+1) = InfectionMatrix(i,j+1)+ RANDOM(4);
InfectionMatrix(i,j-1) = InfectionMatrix(i,j-1)+ RANDOM(5);
InfectionMatrix(i+1,j+1) = InfectionMatrix(i+1,j+1) + RANDOM(6);
InfectionMatrix(i+1,j-1) = InfectionMatrix(i+1,j-1) + RANDOM(7);
InfectionMatrix(i+1,j) = InfectionMatrix(i+1,j) + RANDOM(8);
rng('shuffle')
TooHigh = find(InfectionMatrix > 100);
for m = 1:1:length(TooHigh)
InfectionMatrix(TooHigh(m)) = 100;
end
end
h = heatmap(InfectionMatrix)
old_warning_state = warning('off', 'MATLAB:structOnObject');
hs = struct(h);
warning(old_warning_state);
hs.XAxis.TickValues = [];
hs.YAxis.TickValues = [];
I want to model kind of a simplistic view of a spreading infection. There are 2 things I'd like to accomplish.
Id like to know how to change the spread of the infection to be more circular, there are clearly issues with the corner nodes progressing in a star shape.
Id also like to know how to change the bottom half of the map to progress at half the rate of the top, i.e The Random number generation RANDOMwould be RANDOM/2
That kind of idea.
I'd appreciate any help to improve my code that is not relevant to the problems I specified also.

Answer 1

I'm not sure what you're aiming for but I think you would want to use a 2d convolution of the sort
Infected = zeros(100);
Infected(50,50) = 1;
InfectionMatrix = zeros(100);
for k = 1:90
RANDOM = (b-a).*rand(3,3) + a;
RANDOM(2,2) = 0;
RANDOM = RANDOM .* fspecial('gaussian',3,1); % sigma=1 3x3 kernel
InfectionMatrix = InfectionMatrix + conv2(Infected,RANDOM,'same');
Infected = InfectionMatrix > 0.7;
end
You can modulate the random number by a gaussian filter, like fspecial(), to ensure that they fall off at the corners.