Replace an element in a cell array when a certain value only occurs once?

I have a cell array (x) with varying numbers of elements in each cell. In the instance where there is only one value in a cell (e.g. column 7), I would like to replace with a -1. I have tried a few approaches including these:

for sum = sum(x {i}(:,1) > 0); 

      if sum(1,1) == 1              
          x {i}(:,1) = 0;
      end
  end

and

oout=sum(cellfun(@double,x(:,1:19)))

I would appreciate any help here. Thanks

Answer 1

[Stephen23]

Simpler:

>> a = rand(20,1);
>> c = {a,a,a,a,1,a,a,a,1,a,a,a};
>> c(cellfun(@isscalar,c)) = {-1}

[KL]

Neat!

[Jones]

I wasn't aware of the isscalar function, thanks!

[Stephen23]

"I wasn't aware of the isscalar function, thanks!"

MATLAB has great documentation. Practice using it. In particular:

1. the "See also" links at the bottom of each page for related functions and articles.
2. the contents on the LHS, which are all links to topics and toolboxes.
3. your favorite internet search engine can search the documentation too!

Practice using the documentation. It is the best and only source for knowing how to use MATLAB.

https://www.mathworks.com/matlabcentral/answers/228557-experts-of-matlab-how-did-you-learn-any-advice-for-beginner-intermediate-users

Answer 2

[KL]

a = rand(20,1);
x = {a,a,a,a,1,a,a,a,1,a,a,a};
sizes_x = cellfun(@(e) (size(e,1)*size(e,2))==1,x,'UniformOutput',false)
x(cell2mat(sizes_x)) = {-1};

[Jones]

Thanks a lot, worked perfectly.