COMPCOL - Compare columns of a matrix.

Contents

Description

Compare the columns of A in increasing order (ie, A(:,1) 'is compared to' A(:,2), A(:,2) 'is compared to' A(:,3),...) where the comparison function 'is compared to' is given by the function handled by the string order.

Syntax

     R = COMPCOL(A);
     R = COMPCOL(A,order);

Inputs

A : input matrix whose colums have to be compared; if dims(A)==3, then the matrix A is reshaped so that its elements are compared along the 3rd dimension.

order : optional input string handling the function used for comparing the columns of A; order is either '>', '<', '<=', '>=' or '=='; default: vorder='<'|.

Output

R : a boolean matrix with same number of lines as A stating for each line i of the matrix A if the assertion: A(i,1) order A(i,2) order ... order A(i,ncols) is true or false.

See also

Ressembles: SORT, SORTROWS.

Function implementation

function R = compcol(A,varargin)

parsing the parameters

if ~isnumeric(A)
    error('compcol:inputerror',...
        'a matrix is required in input');
end

p = createParser('COMPCOL');   % create an instance of the inputParser class.
p.addOptional('order', '<', @(x)ischar(x) && ...
    any(strcmpi(x,{'>','<','<=','>=','=='})));

% parse and validate all input arguments
p.parse(varargin{:});
p = getvarParser(p);

internal variables

ndims = nb_dims(A);
[x y ncols] = size(A);
if ndims==2 || ncols==1
    ncols = y;
elseif ndims==3
    A = reshape(A,[x*y ncols]);
    x = x*y;
elseif ndims>3
    error('compcol:inputerror',...
        'cannot process vectors or matrices with dimension>3');
end

% set the order variable to the handle for the comparison function selected
order = str2func(p.order);

testing

% initialize the output image
R = true(x,1); % ones(x,1);

main comparison function

for i=1:ncols-1
    % R = eval(['R & A(:,i)' order 'A(:,i+1)']);
    R = R & order(A(:,i),A(:,i+1));
    % example: if order='<' and A with size ncols=3, this expresion is then
    % equivalent to:
    %     R = A(:,1)<I(:,2) & A(:,2)<I(:3)
end

if ndims==3
    A = reshape(A,[x/y y ncols]);                                      %#ok
    R = reshape(R,[x/y y]);
end

end% end of compcol