Matrix Manipulation of a specific column

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Brady Wayne Robinson 2018-9-27

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https://ww2.mathworks.cn/matlabcentral/answers/420949-matrix-manipulation-of-a-specific-column

评论： Hyeokjin Jho 2018-10-1

I have data in excel that is 17 columns by 4800 rows. The 17 columns represent different muscles, and the rows represent times they are "activated." For each column I need to know which numbers in that column are greater then 10 and what that number is. Once I find all those different numbers I need to sum them up. Just uncertain how to do this. Thank You!

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Answer 1

Hyeokjin Jho 2018-9-27

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https://ww2.mathworks.cn/matlabcentral/answers/420949-matrix-manipulation-of-a-specific-column#answer_338615

在 MATLAB Online 中打开

Assuming Data is the matrix that containing your data,

threshold = 10;
for i = size(Data,2)
    pickedColumn = Data(:,i);
    selectedNumbers{i} = pickedColumn(pickedColumn>threshold);
    summedNumbers(i) = sum(selectedNumbers{i});
end

will work.

Numbers greater than 10 of column i is stored in selectedNumbers{i}, and summed value in summedNumbers(i)

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Brady Wayne Robinson 2018-9-27

This doesn't seem to work. The error I get is Undefined function 'gt' for input arguments of type 'table'.

Error in Matlab_Homework1 (line 16) selectedNumbers{i} = pickedColumn(pickedColumn>threshold);

>>

Hyeokjin Jho 2018-10-1

Apparently Data seems to be a table instead of normal matrix.

threshold = 10;
for i = size(Data,2)
  pickedColumn = Data{:,i};
  selectedNumbers{i} = pickedColumn(pickedColumn>threshold);
  summedNumbers(i) = sum(selectedNumbers{i});
end

To extract data from table, you have to change Data(:,i) to Data{:,i}.

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