卡方检验不成功.zip

function [p, Q]= chi2test(x) % Usage: [p, Q]= chi2test(x) % % The chi-squared test. % % Given a number of samples this function tests the hypothesis that the samples are % independent. If Q > chi2(p, nu), the hypothesis is rejected. % % Each column represents a variables, each row a sample. % % If you find any errors, please let me know: . % % ARGUMENTS: % x Absolut numbers. % p The prob ability value, calculated from Q. % Q The resulting Q-value. % % EXAMPLE 1 % In region A, 324 of 556 cows were red, whereas in region B 98 of 260 were red. % [p, Q]= chi2test([324, 556-324; 98, 260-98]) % p= % 4.2073e-08 % Q= % 30.0515 % With an error risk of about 4e-08, we can claim that the samples are independent. % % EXAMPLE 2 % Throw two different dices to see if they have the same probability of 1 (and 2, 3, 4, 5, 6). % We don't check if they are symetrical, only if the both behave in the same way. % [p,Q] = chi2test([15,10; 7,11; 9,7; 20,15; 26,21; 19,16]) % p= % 0.8200 % Q = % 2.2059 % The dices don't significantly behave differently. That is, they seem to behave in the same way. % % HISTORY: v.1.0, first working version, 2007-08-30. % % COPYRIGHT: (c) 2007 Peder Axensten. Use at own risk. % KEYWORDS: chi-squared test, chi-squared, chi2, test %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Check the arguments. if(nargin ~= 1), error('One and only one argument required!'); end if(ndims(x) ~= 2), error('The argument (x) must be a 2d matrix!'); end if(any(size(x) == 1)), error('The argument (x) must be a 2d matrix!'); end if(any(~isreal(x))), error('All values of the argument (x) must be real values!'); end % Calculate Q = sum( (a-np*)^2/(np*(1-p*)) ) s= size(x, 1); r= size(x, 2); np= sum(x, 2)/sum(sum(x)) * sum(x); % p=sum(x, 2)/sum(sum(x)) and n=sum(x) Q= sum(sum((x-np).^2./(np))); % Calculate cdf of chi-squared to Q. Degrees of freedom, v, is (r-1)*(s-1). p= 1 - gammainc(Q/2, (r-1)*(s-1)/2); end