Processing .mat files via a for loop

Question

Sophia 2023-6-7

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1979479-processing-mat-files-via-a-for-loop

评论： Sophia 2023-6-8

Hi there,

I would like to read in these .mat files and process them via a for loop

Firstly, I need to replace all values above 700 in column 2 (PAR) with NaN

Secondly, I need to find all missing datetimes from column 1 (DateTime) and fill these in (datetime should be running every 5 min), the corresponding value in column 2 can be NaN

I have attempted to create a for loop and believe that the table needs to be converted into a timetable to be able to use greater than (>)?

I am new to for loops, but it would be good to learn how to do all of this processing within the for loop rather than for each separate file.

TIA

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Dyuman Joshi 2023-6-7

在 MATLAB Online 中打开

"Firstly, I need to replace all values above 700 in column 2 (PAR) with NaN"

Use logical indexing.

"I have attempted to create a for loop and believe that the table needs to be converted into a timetable to be able to use greater than (>)?"

Access the elements of table via indexing -

LastName = ["Sanchez";"Johnson";"Zhang";"Diaz";"Brown"];
Age = [38;43;38;40;49];
Smoker = [true;false;true;false;true];
Height = [71;69;64;67;64];
Weight = [176;163;131;133;119];
BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];
patients = table(LastName,Age,Smoker,Height,Weight,BloodPressure)
patients = 5×6 table
    LastName     Age    Smoker    Height    Weight    BloodPressure
    _________    ___    ______    ______    ______    _____________

    "Sanchez"    38     true        71       176       124     93  
    "Johnson"    43     false       69       163       109     77  
    "Zhang"      38     true        64       131       125     83  
    "Diaz"       40     false       67       133       117     75  
    "Brown"      49     true        64       119       122     80  
%Access elements of a column
out=patients.(4)
out = 5×1
    71
    69
    64
    67
    64
%Access a particular element via {}
patients{3,4}
ans = 64
patients{3,2}
ans = 38
patients{3,4}>patients{3,2}
ans = logical
   1

Also, please share your code.

Sophia 2023-6-7

Hi Dyuman,

Thanks for your answer but as I am using files with a lot of data is there not an easier way to access elements of the table without indexing?

The code is attached to my question as a .m file

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Answer 1

Swastik 2023-6-8

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1979479-processing-mat-files-via-a-for-loop#answer_1252264

在 MATLAB Online 中打开

Assuming each MAT-File holds only one variable, we can load it using this

tmpC  = struct2cell(load(filename));
myVar = tmpC{1};

For more information go to this [link](https://in.mathworks.com/matlabcentral/answers/723348-get-unknown-variable-from-mat-file#answer_603208)

I have updated the provided script to load `MAT-File` and process them in the same for loop you are loading them from.

myFolder = 'processing/raw_data';
filePattern = fullfile(myFolder,'PAR_*.mat');
matFiles = dir(filePattern);
for k = 1: length(matFiles)
    matFilename = fullfile(myFolder,matFiles(k).name);
    tmpC  = struct2cell(load(matFilename));
    PAR = tmpC{1};
    PAR = table2timetable(PAR)
    idx = any(PAR{:,:} > 700, 2)
end