Using a loop to add rows to a struct, but the counter overwrites the rows.

Question

Bertrand 2024-5-14

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https://ww2.mathworks.cn/matlabcentral/answers/2118896-using-a-loop-to-add-rows-to-a-struct-but-the-counter-overwrites-the-rows

评论： Bertrand 2024-5-15

I am using this loop, which is embeded in another loop which loads 3 files, to add rows to a struct. After it itterates through 1 files, the rows get overwritten starting from 1. I know this is because of the counter, but I just can't wrap my head around how have it start after the last entry. Any help would be greatly appreciated!

for structRow = 1:nTrials
    masterStruct(structRow).mouse = file.subjectNumber;
    masterStruct(structRow).date = matfiles.name;
    masterStruct(structRow).trialEnd = trials(structRow).trialEnd
    masterStruct(structRow).reactTimeMS = trials(structRow).reactTimeMS;
    masterStruct(structRow).rewardUL = trials(structRow).rewardUL;
    masterStruct(structRow).stimulusType = trial.stimulusType;
    masterStruct(structRow).preStimMS = trial(structRow).preStimMS;
    masterStruct(structRow).visualDurMS = trial(structRow).visualDurMS;
    masterStruct(structRow).optiDurMS = trial(structRow).optiDurMS;
    masterStruct(structRow).minPowerMW = blockInfo(structRow).minPowerMW;
    masterStruct(structRow).maxPowerMW = blockInfo(structRow).maxPowerMW;
    masterStruct(structRow).minContrastPC = blockInfo(structRow).minContrastPC;
    masterStruct(structRow).maxContrastPC = blockInfo(structRow).maxContrastPC;
end

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Answer 1

Torsten 2024-5-14

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编辑：Torsten 2024-5-15

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I don't know how "trial" and "blockInfo" are organized. Here is one suggestion:

for ifile = 1:3
  for s = 1:nTrials
    structRow = (i-1)*nTrials + s;
    masterStruct(structRow).mouse = file.subjectNumber;
    masterStruct(structRow).date = matfiles.name;
    masterStruct(structRow).trialEnd = trials(s).trialEnd
    masterStruct(structRow).reactTimeMS = trials(s).reactTimeMS;
    masterStruct(structRow).rewardUL = trials(s).rewardUL;
    masterStruct(structRow).stimulusType = trial.stimulusType;
    masterStruct(structRow).preStimMS = trial(s).preStimMS;
    masterStruct(structRow).visualDurMS = trial(s).visualDurMS;
    masterStruct(structRow).optiDurMS = trial(s).optiDurMS;
    masterStruct(structRow).minPowerMW = blockInfo(s).minPowerMW;
    masterStruct(structRow).maxPowerMW = blockInfo(s).maxPowerMW;
    masterStruct(structRow).minContrastPC = blockInfo(s).minContrastPC;
    masterStruct(structRow).maxContrastPC = blockInfo(s).maxContrastPC;
  end 
end

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Bertrand 2024-5-15

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Appreciate the response, but this loop is part of a larger loop so i need it to run through the entire large loop then itterate back, here is a brief version of how it is set up.

% Loading of files
matfiles = dir('*.mat') ; 
% Callibration
nFiles = length(matfiles) ; 
masterStruct = struct()
 
for fileNum = 1:nFiles
    load(matfiles(fileNum).name)
nTrials  = length(trials);
for structRow = 1:nTrials
        masterStruct(structRow).mouse = file.subjectNumber;
        masterStruct(structRow).date = matfiles.name;
        masterStruct(structRow).trialEnd = trials(structRow).trialEnd
        masterStruct(structRow).reactTimeMS = trials(structRow).reactTimeMS;
        masterStruct(structRow).rewardUL = trials(structRow).rewardUL;
end
end

Torsten 2024-5-15

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The answer remains almost the same:

structRow = 0;
for fileNum = 1:nFiles
   load(matfiles(fileNum).name)
   nTrials  = length(trials);
   for s = 1:nTrials
        structRow = structRow + 1;
        masterStruct(structRow).mouse = file.subjectNumber;
        masterStruct(structRow).date = matfiles.name;
        masterStruct(structRow).trialEnd = trials(s).trialEnd
        masterStruct(structRow).reactTimeMS = trials(s).reactTimeMS;
        masterStruct(structRow).rewardUL = trials(s).rewardUL;
   end
end

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Answer 2

Shivani 2024-5-15

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Hi @Bertrand,

After analysing the code snippet shared in the question, it is my understanding that you are encountering this error because the index ‘structRow’ used to add rows to ‘masterStruct’ is reset to 1 for each new file processed in the loop. This means that for each file, the code is filling ‘masterStruct’ from the first row again, thereby overwriting the data added from previous files.

This can be resolved by adding a separate counter that does not reset with each new file. Instead, it continuously increments across all files and trials. This way, each new piece of data is added to the next available position in ‘masterStruct’, preventing any overwriting. Kindly refer to the code snippet below for an example on how this can be implemented.

masterStructIndex = 1; 
for fileNum = 1:nFiles 
    load(matfiles(fileNum).name); 
    nTrials = length(trials); 
    for structRow = 1:nTrials 
        masterStruct(masterStructIndex).mouse = file.subjectNumber;   
        masterStruct(masterStructIndex).date = matfiles.name;    
        masterStruct(masterStructIndex).trialEnd = trials(structRow).trialEnd; 
        masterStruct(masterStructIndex).reactTimeMS = trials(structRow).reactTimeMS; 
        masterStruct(masterStructIndex).rewardUL = trials(structRow).rewardUL; 
        
        masterStructIndex = masterStructIndex + 1; 
    end 
end 

Hope this resolves the error encountered!

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Bertrand 2024-5-15

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@Torsten @Shivani

Hey Guys appreciate the responses, both your suggestions are real close. The thing is I have a bunch of preprocessing that happens before this loop in ecountered, so by having it load files again this late indexes data that has not been processed. Here is the entire code if that help. I'm new to MATLAB and just can't seem to wrap my head around this!

% Loading of files
matfiles = dir('*.mat') ; 
% Callibration
nFiles = length(matfiles) ; 
masterStruct = struct()
for fileNum = 1:nFiles
    load(matfiles(fileNum).name)
%% Drop Invalid Trials
keepIdx = ones(length(trials),1);
% Change non usable datapoints to NaN
 for trialNum = 1:length(trials)
  % Check if the 'trialEnd' field is empty
  if isempty(trials(trialNum).trialEnd)
      keepIdx(trialNum) = 0;
  end
  % Only keep eots 0,1,2
  if trials(trialNum).trialEnd > 2
      keepIdx(trialNum) = 0;
  end
end
% Clean Trials 
trials = trials(logical(keepIdx));
clear keepIdx trialNum
%% Clean Up Miss RTs
% Loop through each trial
for trialNum = 1:length(trials)
  % Check if the 'reactTimeMS' field contains a value greater than the threshold
  if trials(trialNum).reactTimeMS > 10000
      % Set the 'reactTimeMS' field to NaN if the condition is met
      trials(trialNum).reactTimeMS = NaN;
  end
end
  %% Extract Basic Results 
  
  % Struct Extraction  
  trial = [trials.trial];
  blockInfo = [trials.blockStatus];
  % Main Field Extraction
  trialEnd = [trials.trialEnd];
  reactTimeMS = [trials.reactTimeMS];
  rewardUL = [trials.rewardUL];
  nTrials  = length(trials);
  % Struct of Outcomes
  indicies.hit   = trialEnd == 0;
  indicies.early = trialEnd == 1;
  indicies.miss  = trialEnd == 2;
  %% Extract Quest data, how should this be incorporated into the master struct.
  % Typically the threshold estimate after 100 trials was the end of block.
  % init array of true
  questIdx = true(length(trials),1);
  
  % QuestTrialID, iterate through trials, check if questResults exists
  for trialNum = 1:length(trials)
    if isempty(trials(trialNum).questResults) % no quest, not a staircase trial
        questIdx(trialNum) = false;
    end
  end
  % Write results to a new 
  quest = [trials(questIdx).questResults];
  %% Write the data to a row of your master struct
  % Better counter needed so it does not write over rows from previous
  % files
  for structRow = 1:nTrials
        masterStruct(structRow).mouse = file.subjectNumber;
        masterStruct(structRow).date = matfiles.name;
        masterStruct(structRow).trialEnd = trials(structRow).trialEnd
        masterStruct(structRow).reactTimeMS = trials(structRow).reactTimeMS;
        masterStruct(structRow).rewardUL = trials(structRow).rewardUL;
        masterStruct(structRow).stimulusType = trial.stimulusType;
        masterStruct(structRow).preStimMS = trial(structRow).preStimMS;
        masterStruct(structRow).visualDurMS = trial(structRow).visualDurMS;
        masterStruct(structRow).optiDurMS = trial(structRow).optiDurMS;
        masterStruct(structRow).minPowerMW = blockInfo(structRow).minPowerMW;
        masterStruct(structRow).maxPowerMW = blockInfo(structRow).maxPowerMW;
        masterStruct(structRow).minContrastPC = blockInfo(structRow).minContrastPC;
        masterStruct(structRow).maxContrastPC = blockInfo(structRow).maxContrastPC;
      
  end
  
end