function [tf,duplicated] = checkDuplicateLabels(obj,labels1,labels2,okLocs)

            %CHECKDUPLICATELABELS Check for duplicated names.

            % Check for any duplicate names in names1            

            if nargin == 2 % checkDuplicateLabels(obj,labels1) 

                % names1 is always a cellstr

                duplicated = false(size(labels1)); 

                [labels1Sorted,lids] = sort(labels1); 

                duplicated(2:end) = strcmp(labels1Sorted(1:end-1),labels1Sorted(2:end)); 

                % Put duplicated back in the original order.

                duplicated(lids) = duplicated;  

            % Check if any name in names1 is already in names2, except that

            % names1(i) may be at names2(okLocs(i)).  This does not check if

            % names1 contains duplicates within itself

            elseif nargin == 4 % checkDuplicateLabels(obj,labels1,labels2,okLocs)

                % names2 is always a cellstr

                if ischar(labels1) % names1 is either a single character vector ...

                    tmp = strcmp(labels1, labels2); tmp(okLocs) = false;

                    duplicated = any(tmp);

                else             % ... or a cell array of character vectors

                    duplicated = false(size(labels1));

                    for i = 1:length(labels1) %#ok<CPROPLC>

                        tmp = strcmp(labels1{i}, labels2); tmp(okLocs(i)) = false;

                        duplicated(i) = any(tmp);

                    end

                end

            % Check if any name in names1 is already in names2.  This does not check if

            % names1 contains duplicates within itself

            else % nargin==3, checkDuplicateLabels(obj,labels1,labels2) - least frequent syntax

                % names2 is always a cellstr

                if ischar(labels1) % names1 is either a single character vector ...

                    duplicated = any(strcmp(labels1, labels2));

                else             % ... or a cell array of character vectors

                    duplicated = false(size(labels1));

                    for i = 1:length(labels1) %#ok<CPROPLC>

                        duplicated(i) = any(strcmp(labels1{i}, labels2));

                    end

                end

            end 

            tf = any(duplicated); 

            if tf && obj.requireUniqueLabels && (nargout == 0) 

                allDups = labels1(duplicated); 

                throwAsCaller(MException(message(obj.DuplicateLabelExceptionID,allDups{1}))); % Report the first dup in the message

            end 

        end