Calculations/Data-Analyzer/StructuralPhaseTransition/SpectralAnalysisRoutines/understandingCumulants.m

224 lines
6.2 KiB
Matlab

%% Main script: Sweep different parameter pairs
% Default parameters
defaults.mu1 = 0.5;
defaults.mu2 = 1.0;
defaults.sigma1 = 0.1;
defaults.sigma2 = 0.1;
defaults.weight1 = 0.5;
% Parameter pair definitions
%{
param_pairs = {
'mu1', linspace(0.7, 1.0, 40), ...
'mu2', linspace(1.0, 1.3, 40);
'mu1', linspace(0.7, 1.0, 40), ...
'weight1', linspace(0.2, 0.8, 40);
'sigma1', linspace(0.05, 0.2, 40), ...
'sigma2', linspace(0.05, 0.2, 40);
'mu1', linspace(0.7, 1.0, 40), ...
'sigma1', linspace(0.05, 0.2, 40);
'mu2', linspace(1.0, 1.3, 40), ...
'weight1', linspace(0.2, 0.8, 40);
};
%}
param_pairs = {
'mu1', linspace(0.1, 1.5, 40), ...
'mu2', linspace(0.1, 1.5, 40);
};
% Cumulant index to visualize (2=variance, 3=skewness, 4=kurtosis)
cumulant_to_plot = 4;
% Run sweep for each pair
for i = 1:size(param_pairs,1)
param1_name = param_pairs{i,1};
param1_vals = param_pairs{i,2};
param2_name = param_pairs{i,3};
param2_vals = param_pairs{i,4};
fprintf('Sweeping %s and %s...\n', param1_name, param2_name);
Z = sweepBimodalCumulants(param1_name, param1_vals, ...
param2_name, param2_vals, ...
defaults, cumulant_to_plot);
end
%%
% Parameters
N_total = 10000;
mu1 = 0.5;
sigma1 = 0.1;
mu2 = 1.0;
sigma2 = 0.1;
weight1 = 0.7;
% Generate data
data = generateBimodalDistribution(N_total, mu1, mu2, sigma1, sigma2, weight1);
% Plot histogram
figure(3);
clf
set(gcf, 'Color', 'w', 'Position', [100 100 950 750]);
histogram(data, 'Normalization', 'pdf', 'EdgeColor', 'none', 'FaceAlpha', 0.5);
hold on;
% Overlay smooth density estimate
[xi, f] = ksdensity(data);
plot(f, xi, 'r-', 'LineWidth', 2);
% Labels and title
xlabel('Value');
ylabel('Probability Density');
legend('Histogram', 'Smoothed Density');
grid on;
%%
N = size(Z, 1);
main_diag_values = diag(Z);
anti_diag_values = diag(flipud(Z));
param1_diag_main = param1_vals;
param2_diag_main = param2_vals;
param1_diag_anti = param1_vals;
param2_diag_anti = flip(param2_vals);
% For example, plot the main diagonal cumulants:
figure(4);
set(gcf, 'Color', 'w', 'Position', [100 100 950 750]);
plot(1:N, main_diag_values, '-o');
xlabel('Index along diagonal');
ylabel('$\kappa_4$', 'Interpreter', 'latex');
title('$\kappa_4$ along anti-diagonal', 'Interpreter', 'latex');
% Plot anti-diagonal cumulants:
figure(5);
set(gcf, 'Color', 'w', 'Position', [100 100 950 750]);
plot(1:N, anti_diag_values, '-o');
xlabel('Index along anti-diagonal');
ylabel('$\kappa_4$', 'Interpreter', 'latex');
title('$\kappa_4$ along anti-diagonal', 'Interpreter', 'latex');
%% === Helper: Bimodal Distribution ===
function data = generateBimodalDistribution(N_total, mu1, mu2, sigma1, sigma2, weight1)
%GENERATEBIMODALDISTRIBUTION Generates a single bimodal distribution.
%
% data = generateBimodalDistribution(N_total, mu1, mu2, sigma1, sigma2, weight1)
%
% Inputs:
% N_total - total number of samples
% mu1, mu2 - means of the two modes
% sigma1, sigma2 - standard deviations of the two modes
% weight1 - fraction of samples from mode 1 (between 0 and 1)
%
% Output:
% data - shuffled samples from the bimodal distribution
% Validate weight
weight1 = min(max(weight1, 0), 1);
weight2 = 1 - weight1;
% Determine number of samples for each mode
N1 = round(N_total * weight1);
N2 = N_total - N1;
% Generate samples
mode1_samples = normrnd(mu1, sigma1, [N1, 1]);
mode2_samples = normrnd(mu2, sigma2, [N2, 1]);
% Combine and shuffle
data = [mode1_samples; mode2_samples];
data = data(randperm(length(data)));
end
%% === Helper: Cumulant Calculation ===
function kappa = computeCumulants(data, max_order)
data = data(:);
mu = mean(data);
centered = data - mu;
% Preallocate
c = zeros(1, max_order);
kappa = zeros(1, max_order);
% Compute central moments up to max_order
for n = 1:max_order
c(n) = mean(centered.^n);
end
% Assign cumulants based on available order
if max_order >= 1, kappa(1) = mu; end
if max_order >= 2, kappa(2) = c(2); end
if max_order >= 3, kappa(3) = c(3); end
if max_order >= 4, kappa(4) = c(4) - 3*c(2)^2; end
if max_order >= 5, kappa(5) = c(5) - 10*c(3)*c(2); end
if max_order >= 6
kappa(6) = c(6) - 15*c(4)*c(2) - 10*c(3)^2 + 30*c(2)^3;
end
end
%% === Helper: Cumulant Calculation ===
function Z = sweepBimodalCumulants(param1_name, param1_vals, ...
param2_name, param2_vals, ...
fixed_params, ...
cumulant_index)
%SWEEPBIMODALCUMULANTS Sweep 2 parameters and return a chosen cumulant.
%
% Z = sweepBimodalCumulants(...)
% Returns a matrix Z of cumulant values at each grid point.
% Setup grid
[P1, P2] = meshgrid(param1_vals, param2_vals);
Z = zeros(size(P1));
N_samples = 1000;
maxOrder = max(4, cumulant_index);
for i = 1:numel(P1)
% Copy fixed parameters
params = fixed_params;
% Override swept parameters
params.(param1_name) = P1(i);
params.(param2_name) = P2(i);
% Generate and compute cumulants
data = generateBimodalDistribution(N_samples, ...
params.mu1, params.mu2, ...
params.sigma1, params.sigma2, ...
params.weight1);
kappa = computeCumulants(data, maxOrder);
Z(i) = kappa(cumulant_index);
end
% Plot full heatmap
figure;
set(gcf, 'Color', 'w', 'Position', [100 100 950 750]);
imagesc(param1_vals, param2_vals, Z);
set(gca, 'YDir', 'normal');
xlabel(param1_name);
ylabel(param2_name);
title(['Cumulant \kappa_', num2str(cumulant_index)]);
colorbar;
axis tight;
% Optional binary colormap (red = ≥0, blue = <0)
figure;
set(gcf, 'Color', 'w', 'Position', [100 100 950 750]);
imagesc(param1_vals, param2_vals, Z);
set(gca, 'YDir', 'normal');
xlabel(param1_name);
ylabel(param2_name);
title(['Binary color split of \kappa_', num2str(cumulant_index)]);
clim([-1 1]);
colormap([0 0 1; 1 0 0]); % Blue (neg), Red (pos & zero)
colorbar;
axis tight;
end