Creating a Word Index Structure Array

I am working on problem 2 in the attached PDF. When I run this right now, I get an error in my first conditional for if the word is not in the index. How do I say that the word does not exist in the index? Any other problems?

function Index = InsertDoc(Index, newDoc, DocNum)
IndexWords = {Index.Word};
for i = 1:numel(newDoc)
   % If word is not in the Index
    if isempty(Index) || Index(i).Words ~= IndexWords
       Index(numel(IndexWords)+1).Word = newDoc{i};
       Index(numel(IndexWords)+1).Documents = DocNum;
       Index(numel(IndexWords)+1).Locations{end+1} = i;
    else
    end
    % If the word does exist in the Index, but the occurance is unknown
    % 1st occurance
    if Index(i).Documents == DocNum
        WordInIndex = strcmpi(newDoc{i},{Index.Word});
        Index(WordInIndex).Documents = [Index(WordInIndex).Documents,DocNum];
        Index(WordInIndex).Locations{end}(end+1)=i
      % 2nd occurance or later
    else
        Index(WordInIndex.Locations{numel(Index(WordInIndex).Locations)+1}) = i;
    end
end

Answer 1

[Image Analyst]

You didn't attach anything. But you might look at the ismember() and isempty() functions.

[Rick]

My bad, I attached it now

[Image Analyst]

I don't really know what you want to do. Do you think you can use either of those two functions?