Invalid data type - converting to cell array to run functions

I essentially want to pull the data from timepoints of interest and run the same functions for each "bout of data" even though these bouts are not always the same length. I understand a cell array will be helpful for this, but when I try to write for loop, the data is no longer in 'double' form to perform functions.

How can I convert to cell array but keep the data in 'double' type?

Example failure 1

% tot_dff: vector of data across time

%f_i & f_o : variables corresponding to time on and off for periods of interest in the data

for i=1:length(f_i);

dff{i} = num2cell(tot_dff(1,f_i(i):f_o(i)));

end

X = cellfun(@mean,dff);

Y = cellfun(@max,dff);

Error using sum

Invalid data type. First argument must be numeric or logical.

% In this case dff is 1x46 cell which each cell containing cells corresponding to each data point.

Example failure 2

for i =1:length(f_i);

dff{i} = {tot_dff(1,f_i(i):f_o(i))};

end

X=cellfun(@mean,dff);

Y=cellfun(@max,dff);

%in this case, dff is 1x46 cell array with each cell containing my list of numbers in [ ] . Still can't run the functions on it and get the same error.

When I create my cell array by hand

dff = {tot_dff(1:3),tot_dff(6:10)} ........ this works but will take me forever!

Thank you for your help!

Answer 1

[Stephen23]

In both cases your code nests a cell array inside a cell array:

 dff{i} = num2cell(tot_dff(1,f_i(i):f_o(i)));
 %        ^^^^^^^^^                        ^ % define the RHS as a cell array
 %  ^ ^                                      % place the RHS in another cell array

The nesting is superfluous, you only need one cell array (on the LHS), e.g.:

nml = length(f_i);
dff = cell(1,nml); % preallocate!
for k = 1:nml;
    dff{k} = tot_dff(1,f_i(k):f_o(k));
end       % ^                        ^ do NOT make this a cell array !

[Emma Janke]

Thank you so much!