Help with appending onto a table in a loop

Question

James McBrearty 2022-8-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1787575-help-with-appending-onto-a-table-in-a-loop

评论： James McBrearty 2022-8-31

Hi All,

I have a bit of code where I am trying to create a table in a loop, appending on as each loop passes. No matter what way I try it, it only shows up with the last iteration, rather than the whole amount. Would anyone be able to help? Here is the code:

sqlTable = table;
sqlTableTemp = table;
% Doing for all non-adjusted
for i = 1:length(numModels)
    sqlTableTemp.forecastType = repmat(forecastType,length(periodEnd),1);
    sqlTableTemp.forecastName = repmat(forecastName,length(periodEnd),1);
    sqlTableTemp.modelName = repmat(modelNames{i}, length(periodEnd),1);
    sqlTableTemp.createDate = repmat(createDate,length(periodEnd),1);
    sqlTableTemp.createTime = repmat(createTime,length(periodEnd),1);
    sqlTableTemp.creator = repmat(creator,length(periodEnd),1);
    sqlTableTemp.activeForecast = zeros(length(periodEnd),1);
    sqlTableTemp.periodEnding = periodEnd;
    sqlTableTemp.val = cell2mat(app.ForecastResultsTable.UserData(:,i+1));
    sqlTable = [sqlTable;sqlTableTemp];
end

All comments and help would be appreciated.

Thanks, James

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Cris LaPierre 2022-8-26

在 MATLAB Online 中打开

Can you share an your variables? I can't duplicate with this example

LastName = {'Sanchez';'Johnson';'Li';'Diaz';'Brown'};
Age = [38;43;38;40;49];
Smoker = logical([1;0;1;0;1]);
Height = [71;69;64;67;64];
Weight = [176;163;131;133;119];
BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];
T = table(LastName,Age,Smoker,Height,Weight,BloodPressure)
T = 5×6 table
     LastName      Age    Smoker    Height    Weight    BloodPressure
    ___________    ___    ______    ______    ______    _____________

    {'Sanchez'}    38     true        71       176       124     93  
    {'Johnson'}    43     false       69       163       109     77  
    {'Li'     }    38     true        64       131       125     83  
    {'Diaz'   }    40     false       67       133       117     75  
    {'Brown'  }    49     true        64       119       122     80  
sqlTable = T(1,:)
sqlTable = 1×6 table
     LastName      Age    Smoker    Height    Weight    BloodPressure
    ___________    ___    ______    ______    ______    _____________

    {'Sanchez'}    38     true        71       176       124     93  
sqlTableTemp = T(1,:);
% Doing for all non-adjusted
for i = 2:height(T)
    sqlTableTemp.LastName = LastName(i);
    sqlTableTemp.Age = Age(i);
    sqlTableTemp.Smoker = Smoker(i);
    sqlTableTemp.Height = Height(i);
    sqlTableTemp.Weight = Weight(i);
    sqlTableTemp.BloodPressure = BloodPressure(i,:);
    sqlTable = [sqlTable;sqlTableTemp];
end
sqlTable
sqlTable = 5×6 table
     LastName      Age    Smoker    Height    Weight    BloodPressure
    ___________    ___    ______    ______    ______    _____________

    {'Sanchez'}    38     true        71       176       124     93  
    {'Johnson'}    43     false       69       163       109     77  
    {'Li'     }    38     true        64       131       125     83  
    {'Diaz'   }    40     false       67       133       117     75  
    {'Brown'  }    49     true        64       119       122     80  

dpb 2022-8-31

The value of numModels over which you're looping is still undefined with the attached -- as are all the RH side variables given.

We can't even try to duplicate the example code but at least two have illustrated that the catenation would work as expected if the loop runs multiple times.

I'm with @Image Analyst, however, that it's probable the table can be built from the data directly instead, IF we could see what the starting data are instead...

James McBrearty 2022-8-31

在 MATLAB Online 中打开

So yeah, it was a bit of an error on my part. numModels was a number that was defined earlier in the source code. I forgot about this, and was trying for find the size of the original array. It was all fixed by changing the original for loop to be

for i=1:numModels
    
end

All of the code works fine now, and is 250 times faster for sql entry than the original code that was used.

Thanks for all the help everyone

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Answer 1

Image Analyst 2022-8-26

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https://ww2.mathworks.cn/matlabcentral/answers/1787575-help-with-appending-onto-a-table-in-a-loop#answer_1034805

在 MATLAB Online 中打开

Why not just do

val = cell2mat(app.ForecastResultsTable.UserData(:,i+1)); % Or whatever.
sqlTable = table(forecastType(:), forecastName(:), modelNames(:), createDate(:), ...
createTime(:), creator(:), activeForecast(:), periodEnding(:), val(:), 
'VariableNames', {'forecastType', 'forecastName', 'modelNames', 'createDate', ...
'createTime', 'creator', 'activeForecast', 'periodEnding', 'val'});