mean of tables in cells

Hello everyone

For a project, I made some measurements, which I want to edit in Matlab. Since the table height is of different length, I want to fill the rest of the tables with NaN. But that doesn't work like I want to. Tables are stored in cells.

for k=1:length(Values)
   
    while height(Values{1,k}) < 51
        
        E = NaN*ones(1,2);
        Values{1,k} = [Values{1,k};E];
    end
end

The other problem occurs, when I want to calculate the mean.

for k=1:length(Values)
    A(k)=mean(Values{1,k}(:,2));
end

I get this error:

Error using sum
Invalid data type. First argument must be numeric or logical.

Error in mean (line 127)
        y = sum(x, dim, flag) ./ mysize(x,dim);

Error in mittelwertbildung_22a (line 8)
    A(k)=mean(Values{1,k}(:,2));

The first value is definitely a numeric value. So I don't know, where the problem is. I appreciate every help I can get. Thanks in advance guys

[KSSV]

Values{1,k}(:,2)

The above is not giving you numbers...so the error. Check it's class.

[Guillaume]

Are your Values{k} actual matlab tables or are they plain matrices. The code you've posted would not work with actual tables.

A few notes:

• don't use 2D notation if your cell array is a vector. Use Values{k} instead of Values{1, k}. The former will work whether Values is a column or row vector, the latter will error. It's also shorter to type.
• E= NaN*ones(1, 2), is a slower way of generating E = NaN(1, 2). To make your code future proof it would be better to make that NaN matrix the same width as the matrix you're appending it to, so even better would be

E = NaN(1, size(Values{k}, 2));

• I'd recommend you use numel instead of length. Then it really doesn't matter whether Values is a row cell array, a column cell array or even a ND cell array.

With regards to your question, what is the output of

cellfun(@isnumeric, Values)

[Fabrice Lambert]

I have a similar problem. Using the OP's example, Values{1,k}(:,2) is a table, so not a valid input for mean. However, mean(Values{1,k}{:,2}) does not work either. How do you (one line) extract data from a table within a cell to do statistics on them, without using table2array etc.?

Answer 1

[Adam Danz]

You can adapt this functional demo to your needs and if it doesn't work with your data, please tell us how your data differ from the demo data.

Values = {table((1:20)',(1:20)'); table((1:22)',(1:22)')};
dth = 26; %desired table height   (51 in your case)

A = zeros(size(Values)); 
for k = 1:length(Values)
    nanpad = array2table(nan(26-height(Values{k}),width(Values{k})), ... 
        'VariableNames',Values{k}.Properties.VariableNames); 
    Values{k} = [Values{k};nanpad];
    A(k) = mean(Values{k}{:,2},'omitnan');
end