finding the average from csv file

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Raushan
Raushan 2023-1-10
编辑： Cris LaPierre 2023-1-20
Hi,
I have several csv file and each file has several columns with the name of ''x'', "y", "u", "v", "exx" like that. I want to read exx from each csv file and find the average of each. For example if I have 10 csv file then I will have 10 columns of exx so I want to find the average of ecah exx column so that at the end I will have 10 values of exx. Now I want to plot the average.
I am doing something like this but it shows concatanation error. can you please help me to figure out.
Folder='G:\Image\';
mat = dir(fullfile(Folder, '*.csv'));
% disp(mat)
% for files_i = 1:length(mat)
% disp(mat(files_i).name)
% data = fullfile(Folder,mat(files_i).name);
% ReadCSV(data,files_i);
%
% end
uall = [];
for files_i = 1:length(mat)
data = fullfile(Folder,mat(files_i).name);
x = readtable(data);
exxall =[exxall x.exx];
end
Any help will be appriciated!

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Cris LaPierre
Cris LaPierre 2023-1-10
Ran in:
There are some mistakes with your code, but the core elements are all there.
  • create exxall as an empty array. You currently create an unused variable, uall
  • You csv files do not all have the same length, so you will get an error when trying to concatenate them. Create exxall as the mean of x.exx to get around this.
Folder='./';
mat = dir(fullfile(Folder, '*.csv'));
exxall = [];
for files_i = 1:length(mat)
data = fullfile(mat(files_i).folder,mat(files_i).name);
x = readtable(data);
exxall =[exxall mean(x.exx)];
end
exxall
exxall = 1×10
0 0.0192 0.0212 0.0084 0.0052 0.0224 0.0176 0.0113 0.0073 0.0270
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Cris LaPierre
Cris LaPierre 2023-1-12
Ran in:
That is one approach. Here's another.that doesn't require predetermining the number of rows to use. By specifying the rows to assign to, it automatically increases the size of the array. When it does this, it adds NaN to the other columns.
NaNs can have an impact when taking a mean, so be sure to set the nanflag property of mean to either include or omit nans in the calculation.
mat = dir('*.csv');
uall = [];
xall = [];
for files_i = 1:length(mat)
X = readtable(mat(files_i).name);
uall(1:height(X)-1,files_i) = diff(X.u);
xall(1:height(X)-1,files_i) = diff(X.x);
end
A = uall./xall;
% Inspect the first 5 rows
A(1:5,:)
ans = 5×10
0 0.0314 0.0170 0.0017 0.0063 0.0262 0.0123 0.0039 -0.0037 -0.0018 0 0.0326 0.0197 0.0111 0.0121 0.0200 0.0131 0.0088 0.0078 0.0184 0 0.0282 0.0187 0.0136 0.0113 0.0208 0.0195 0.0106 0.0126 0.0180 0 0.0253 0.0206 0.0172 0.0143 0.0191 0.0202 0.0144 0.0152 0.0191 0 0.0152 0.0158 0.0164 0.0123 0.0174 0.0139 0.0133 0.0056 0.0180
% Inspect the lasst 5 rows
A(end-4:end,:)
ans = 5×10
0 0.0105 0.0203 0.0158 0.0072 0.0113 0.0162 0.0157 0.0149 0.0233 0 0.0015 0.0026 0.0102 0.0066 0.0161 0.0196 -0.0056 0.0021 0.0345 0 0.0229 0.0126 0.0016 -0.0044 0.0329 0.0037 -0.0040 0.0035 0.0275 0 0.0018 0.0012 0.0055 0.0015 0.0265 0.0131 NaN NaN 0.0205 0 0.0081 0.0049 NaN NaN 0.0329 NaN NaN NaN 0.0251
Raushan
Raushan 2023-1-19
Thank you so much for showing me another method too. I really appreciate this.

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