s_studentt.m

进行T分布检验

% this script familiarizes the user with some basic properties of the
% Student t distribution, see "Risk and Asset Allocation"-Springer (2005), by A. Meucci
% Section 1.3.4

clear; clc; close all;
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% inputs
mu=0;
sigma_2=1;  
nu=1;  % 
NumSimulations=100000;

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% compute pdf and cdf using matlab functions
sigma=sqrt(sigma_2);
x=[mu-4*sigma : sigma/100 : mu+4*sigma]; % set range
pdf =1/sigma*tpdf((x-mu)/sigma,nu);
cdf =tcdf((x-mu)/sigma,nu);

% generate sample using matlab functions
X = mu+sigma*trnd(nu,NumSimulations,1);

% compute quantile using matlab functions
u=[.01 : .01 : .99]; % set range
quantile = mu+sigma*tinv(u,nu);

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% plots
figure
NumBins=round(10*log(NumSimulations));
hist(X,NumBins)
[n,Ds]=hist(X,NumBins);
D=Ds(2)-Ds(1);
hold on
h=plot(x,pdf*NumSimulations*D,'r');
grid on
title('pdf/histogram')

figure
plot([1:NumSimulations],X,'.')
grid on
title('sample vs. observation time')

%break
figure
h=plot(x,cdf,'b');
grid on
title('cdf')

figure
h=plot(u,quantile,'b');
grid on
title('quantile')