Reference to non-existent field

I can't work out why I keep getting reference to non-existent field. I've defined t_accData and I can't see that it is used in any other function so I'm confused:

%% Load data, sample at multiple rates, save resulting as separate CSV files:
 
%Check to see if this step has been completed and saved previously
%If it has, load saved mat file to speed up processing
 
Fs = [400 200 100 50 25]; %Arranging from High to low could be better for some plots
 
%resample in loop
for j = 1:length(Fs)
    %Get current sample rate within loop
    c_rate = Fs(j);
    
    %Check whether file exists (within the for loop)
    if ~exist([filename(1:end-4) '_resample_rawData_Fs_' num2str(c_rate) 'hz.mat'],'file');
        
        %If the file doe not exist, create it: 
        %load acc data into a structure array with fields
        % time, timestamp, x y z, sampleRate;  
        t_accData = resampleCWA(filename, c_rate); %#ok<*AGROW>
        
        %Save t_accData to a Mat file
        save ([filename(1:end-4) '_resample_rawData_Fs_' num2str(c_rate) 'hz.mat', 't_accData'], 't_accData');
        
        %Takes all files of t_accData and combines them into one structure
        %with all sample frequencies within it. The delets t_accData. 
        c_accData(j) = t_accData;
       
    else
        %If the file does exist,  load the existing file containing variable
        %'c_accData'
        tempStruct = load([filename(1:end-4) '_resample_rawData_Fs_' num2str(c_rate) 'hz.mat']);
        c_accData(j) = tempStruct.t_accData;
        clear tempStruct;
        
    end %end of 'If/else' section
end %end of loading 'for loop

[Matt J]

Well, what does dbstop say? It should, for example, let you easily verify whether tempStruct does indeed posssess a field called t_accData.

[Walter Roberson]

You appear to be hitting the branch where the file already exists. You should re-check whether the file contains the variable c_accData like the comment says, or if it contains t_accData like you try to access.

Note: we recommend that you assign

filename = [filename(1:end-4) '_resample_rawData_Fs_' num2str(c_rate) 'hz.mat'];

and then use the variable, instead of rebuilding the name every time you use it.

[Stephen23]

I would recommend that you replace

filename(1:end-4)

with the more robust

[~,F] = fileparts(filename)

Also replace all of those string concatenations with sprintf, which would make it easier to spot bugs, such as this strange filename input to save:

[filename(1:end-4) '_resample_rawData_Fs_' num2str(c_rate) 'hz.mat', 't_accData']

Most probably you did not want that trailing t_accData in the file extension. Better:

sprintf('%s_resample_rawData_Fs_%dhz.mat',F,c_rate)

[Justine Pearce]

Thank you everyone! It now seems to be working with out errors! I'm new to coding so really appreciate your help and advice on writing style too thank you!