Datatype in corr2

Rajashree Annapillai

2019 3 15

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9 次查看（30 天）

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Why the input data is converted to "Double" datatype before finding the correlation coefficient?Please help me to find the answer.

function r = corr2(varargin)
%CORR2 2-D correlation coefficient.
%   R = CORR2(A,B) computes the correlation coefficient between A
%   and B, where A and B are matrices or vectors of the same size.
%
%   Class Support
%   -------------
%   A and B can be numeric or logical. 
%   R is a scalar double.
%
%   Example
%   -------
%   I = imread('pout.tif');
%   J = medfilt2(I);
%   R = corr2(I,J)
%
%   See also CORRCOEF, STD2.
%   Copyright 1992-2013 The MathWorks, Inc.
[a,b] = ParseInputs(varargin{:});
a = a - mean2(a);
b = b - mean2(b);
r = sum(sum(a.*b))/sqrt(sum(sum(a.*a))*sum(sum(b.*b)));
%--------------------------------------------------------
function [A,B] = ParseInputs(varargin)
narginchk(2,2);
A = varargin{1};
B = varargin{2};
validateattributes(A, {'logical' 'numeric'}, {'real','2d'}, mfilename, 'A', 1);
validateattributes(B, {'logical' 'numeric'}, {'real','2d'}, mfilename, 'B', 2);
if any(size(A)~=size(B))
    error(message('images:corr2:notSameSize'))
end
if (~isa(A,'double'))
    A = double(A);
end
if (~isa(B,'double'))
    B = double(B);
end