How to calculate the mean/median/Standard deviation for each column in a table

Here I have table has 716rows*9 coloumns called Analysis1 as shown in figure1.

I would like to each the following steps:

1. The calcualtions for n number of files like this in a folder
2. The formula should be calculated for each coulmn (not for rows) and all the values shoul be store in a one seperate file so that I can plot a graph

I have tried the formula using median(Analysis1) but showing the permute error as shown in figure 2.

I have suceeded applying the formula for an individual coulumn like as shown in figure2:

1. Result1 = median(Analysis.Time)
2. Result2 = median(Analysis.TempL1)

Any suggestion would be appreciated to solve this issue. Thanks in advance.

Answer 1

[Steven Lord]

Let's look at a sample table.

load patients
T = table(LastName, Smoker, Height, Weight, Systolic, Diastolic);
head(T)

ans = 8x6 table
      LastName      Smoker    Height    Weight    Systolic    Diastolic
    ____________    ______    ______    ______    ________    _________

    {'Smith'   }    true        71       176        124          93    
    {'Johnson' }    false       69       163        109          77    
    {'Williams'}    false       64       131        125          83    
    {'Jones'   }    false       67       133        117          75    
    {'Brown'   }    false       64       119        122          80    
    {'Davis'   }    false       68       142        121          70    
    {'Miller'  }    true        64       142        130          88    
    {'Wilson'  }    false       68       180        115          82    

It makes sense to compute the mean for four variables in this table, but not for the LastName or Smoker variables.

M = varfun(@mean, T, 'InputVariables', @isnumeric)

M = 1x4 table
    mean_Height    mean_Weight    mean_Systolic    mean_Diastolic
    ___________    ___________    _____________    ______________

       67.07           154           122.78            82.96     

This looks for all the variables in T for which isnumeric returns true and calls mean on those variables.

[Nagamani Yaadavalli]

Thank you very much Mr. Steven !! This is works for an individual file.

Answer 2

[Image Analyst]

Did you try something like this (untested)

m = table2array(yourTable); % Convert table to regular matrix.
columnMeans = mean(m, 1); % Get the mean of each column in the matrix.

[Image Analyst]

Attach Analysis1 if you still have trouble:

save('answers.mat', 'Analysis1');

Then use the paper clip icon to attach answers.mat.

[Nagamani Yaadavalli]

No, but. I always work with tables. Does it work when I insert this code before the next code.

sometimes I will write in a loop.

[Image Analyst]

You can throw away (clear) the temporary variable m if you want.

clear('m'); % Remove m from memory.

Or you can skip creating the temporary variable at all if you want:

columnMeans = mean(table2array(yourTable), 1); % Get the mean of each column in the table.

Yes, it will work in a loop.

If you want the means to be in a column vector instead of a row vector, you can do this:

columnMeans = columnMeans'; % Make into column vector.

To save, you can use writematrix

writematrix(columnMeans, filename);

Or use some other function like csvwrite(), fprintf(), or whatever.

[Nagamani Yaadavalli]

Thanks, I will try that!

[Nagamani Yaadavalli]

% getting the folder directory of files you want to work
myFolder = '/Users/xxxxxxx/Desktop/Tests/27.11.2020 csv/Total';
% code for determining the file pattern that you have, * represents all the
% files
filePattern = fullfile(myFolder, '*.csv');
% code for addressing all the files
theFiles = dir(filePattern);
for k = 1: length(theFiles)
    baseFileName = theFiles(k).name;
    fullfilename = fullfile(theFiles(k).folder,baseFileName)
    fprintf(1,fullfilename);
    Test= dlmread(fullfilename,',',1,2)
    coloumnMeans = mean(Test,1)
    coloumnMeans = coloumnMeans'
    writematrix(coloumnMeans,mfilename)
end

Hello there !!

As you suggested I have modified the code some how and I got all the results I need. But only one thing left is all the result values are not saving in one file even after using for loop. Here I have considered 4 files in a folder. So that I have all the mean value result in 4 outputs. For example as shown in figure1 it repersents on file output values. How can I get all the outputs in one file as in code or is there any way to save them like that. Could you please look at my code and make some corrections here. Thanks in advance.

[Image Analyst]

Don't use mfilename. Create a new file for the output workbook

[f, baseFileNameNoExt, ext] = fileparts(baseFileName);
baseFileName = sprintf('%s.xlsx', baseFileNameNoExt);
fullWorkBookFileName = fullfile(theFiles(k).folder, baseFileName)
writematrix(coloumnMeans, fullWorkBookFileName)

[Nagamani Yaadavalli]

Thanks for responding. I am not perfect in coding. Culd you please explain about this code whether to continue or modify somewhere ?? Please give me some explanations, so that I can understand.

Note: The files are CSV files

[Image Analyst]

Good point. Usually I put in way more comments. If I were writing this for my company (where other people may have to maintain this code), this is how I'd write it:

% Specify the folder (directory) of CSV files that you want to process.
myFolder = '/Users/xxxxxxx/Desktop/Tests/27.11.2020 csv/Total';
% Get a wildcard pattern so we can get a list of all CSV files in the folder.
filePattern = fullfile(myFolder, '*.csv');
% Below is the code for looping over all the files, reading them in,
% computing the column means, and writing that to an output workbook
% (one output .XLSX file for each input .CSV file).
theFiles = dir(filePattern); % This is a structure.
for k = 1: length(theFiles)
	baseFileName = theFiles(k).name;
	fullInputCSVFileName = fullfile(theFiles(k).folder, baseFileName);
	fprintf('Processing %s...\n', fullInputCSVFileName);
	% Read this matrix from the csv file.
	thisMatrix = dlmread(fullInputCSVFileName,',',1,2);
	% Get the means of each column.
	columnMeans = mean(thisMatrix,1);
	% Convert from a row vector to a column vector because that's how he wants the output file.
	columnMeans = columnMeans';
	% Create a name for the output Excel workbook.
	% We'll use the same base file name but replace the extension by .xlsx.
	[f, baseFileNameNoExt, ext] = fileparts(baseFileName);
	baseFileName = sprintf('%s.xlsx', baseFileNameNoExt);
	% Prepend the folder to get the full file name.
	fullWorkBookFileName = fullfile(theFiles(k).folder, baseFileName);
	% Write the output workbook.
	fprintf('Writing output Excel workbook : %s...\n', fullWorkBookFileName);
	writematrix(columnMeans, fullWorkBookFileName)
end
% Alert user that we're done.
message = sprintf('Done processeing %d CSV files.\n', length(theFiles));
uiwait(msgbox(message));

[Nagamani Yaadavalli]

Thank you for your time and patience. This code is working actually. What happening is all the output results are saving like individual files in the same folder. But the problem is again I have to spent time on that files to put together all the results. Moreover, I have lot of files to do this in future. I am attatching the files I am mentioning here. You can try now easily... Anyways, I appriciate your efforts towards my works. Thanks alot.

[Image Analyst]

If you want only one workbook for all the results, do this:

% Specify the folder (directory) of CSV files that you want to process.
myFolder = '/Users/xxxxxxx/Desktop/Tests/27.11.2020 csv/Total';
% Get a wildcard pattern so we can get a list of all CSV files in the folder.
filePattern = fullfile(myFolder, '*.csv');
% Below is the code for looping over all the files, reading them in,
% computing the column means, and writing that to an output workbook
% (one output .XLSX file for each input .CSV file).
theFiles = dir(filePattern); % This is a structure.
% Make a 2-D array to hold all the column means
columnMeans = zeros(9, length(theFiles)); % One column for each file.
for k = 1: length(theFiles)
	baseFileName = theFiles(k).name;
	fullInputCSVFileName = fullfile(theFiles(k).folder, baseFileName);
	fprintf('Processing %s...\n', fullInputCSVFileName);
	% Read this matrix from the csv file.
	thisMatrix = dlmread(fullInputCSVFileName,',',1,2);
	% Get the means of each column.
	theMeans = mean(thisMatrix,1);
	% Convert from a row vector to a column vector because that's how he wants the output file.
	columnMeans(:, k) = theMeans'; % Add this column vector to the 2-D array.
end
% Create a name for the output Excel workbook.
baseFileName = 'Column Means.xlsx'; % Whatever you want to call it
% Prepend the folder to get the full file name.
fullWorkBookFileName = fullfile(myFolder, baseFileName);
% Write the output workbook.
fprintf('Writing output Excel workbook : %s...\n', fullWorkBookFileName);
writematrix(columnMeans, fullWorkBookFileName)
% Alert user that we're done.
message = sprintf('Done processeing %d CSV files.\n', length(theFiles));
uiwait(msgbox(message));

[Nagamani Yaadavalli]

I tried with this code !! The previous csv files data also changing. So that I tried the below code from your suggesstions. It works great, Thanks for all the suggestions. The output as shown in figure !!

% getting the folder directory of files you want to work
myFolder = '/Users/xxxxxxx/Desktop/xxxxxx/Tests/27.11.2020 csv/Total';
% code for determining the file pattern that you have, * represents all the
% files
filePattern = fullfile(myFolder, '*.csv');
% code for addressing all the files
theFiles = dir(filePattern)
for k = 1: length(theFiles)
    baseFileName = theFiles(k).name;
    fullfilename = fullfile(theFiles(k).folder,baseFileName)
    fprintf(1,fullfilename);
    Test= dlmread(fullfilename,',',1,2)
    theMeans = mean(Test,1)  
end
Analysis1(:,k) = theMeans'