Write a loop to iteratively import files from a folder and do calculations with them

I apologize in advance if some questions I will ask will be trivial, but unfortunately I'm still a beginner.

I have a folder with 500 csv files, called "pressure_export_R1_Blade_tstep_*number*", where the numbers are even (0-2-4-6 ... 998).

I have to write a script that iteratively takes an oscillation period of my blade, corresponding to 50 of these files, and for each of the 50 files (time-step) it must import the information present in the CSV columns and perform some calculations. At the end of the iteration the period must move forward by a time-step (if the first period took files from 0 to 98, the second must take those from 2 to 100 and so on) and the cycle must repeat itself.

My professor gave me some completely unrelated examples, and I'm having difficulty with the first part of the script, the one responsible for defining the path and importing the data.

Here are the snippets:

clear all

close all

clc

bladestring={'blade_1'};

blade=1;

path_csv=[path_write_csv '/pressure_export_blade_' bladestring{blade} '_tstep_' num2str(tstep_vec(tstep)) '.csv'];

% importdata from .csv

for iperiods=1:nperiods

for tstep=1:5

%read data from file and convert to vector and matrices

A_XYZ=importdata(path_csv,delimiter,headerlines);

CFX_Nodes(:,:,tstep,iperiods) = A_XYZ.data(:,1:3);

CFX_Pressure_mat(:,tstep,iperiods)=A_XYZ.data(:,5);

CFX_Normal_mat(:,:,tstep,iperiods)=A_XYZ.data(:,7:9);

CFX_Area_mat(:,tstep,iperiods)=A_XYZ.data(:,6);

CFX_Mesh_Velocity(:,:,tstep,iperiods)=A_XYZ.data(:,10:12);

CFX_Mesh_Disp(:,:,tstep,iperiods)=A_XYZ.data(:,13:15);

end

end

tstep_mat(:,tstep,iperiods)=tstep*trnwrite*timestep;

% calculate work per cycle

work_cycle_X_time=(sum(CFX_Pressure_mat_time.*CFX_Velocity_X_time.*CFX_Normal_X_time.*CFX_Area_mat_time));

work_cycle_Y_time=(sum(CFX_Pressure_mat_time.*CFX_Velocity_Y_time.*CFX_Normal_Y_time.*CFX_Area_mat_time));

work_cycle_Z_time=(sum(CFX_Pressure_mat_time.*CFX_Velocity_Z_time.*CFX_Normal_Z_time.*CFX_Area_mat_time));

work_cycle_time(:,:,:,iperiod)=work_cycle_X_time+work_cycle_Y_time+work_cycle_Z_time;

%integration timestep-wise

tstep_int=tstep_mat_time(1,:,1)';

for blade=1:length(STACst.blade_data_names)

work_cycle_X_int(:,blade)=trapz( tstep_int,work_cycle_X_time(:,:,blade),2);

work_cycle_Y_int(:,blade)=trapz( tstep_int,work_cycle_Y_time(:,:,blade),2);

work_cycle_Z_int(:,blade)=trapz( tstep_int,work_cycle_Z_time(:,:,blade),2);

end

% sum work for each coordinate direction

work_cycle_time_blades(:,iperiod)=work_cycle_X_int+work_cycle_Y_int+work_cycle_Z_int

Thanks to those who will help me!

Answer 1

[Abhishek]

Hi,

I assume that you have a working directory containing numbered .csv files that you want to import and work upon in sets in MATLAB.

This can be accomplished by going to the folder and retrieving the .csv files. Then iterate over those to select the necessary ones and extract the data for further processing.

Here is a sample code you can refer:

%Getting all files into an struct
csv_files = dir(fullfile('path\to\folder', '*.csv'));

%Store count of files in 'Nf'
Nf = length(csv_files);

%Process 'N' files at a time
N=50;

for i=0:Nf-N
    
    %Create a cell array 'batchTable' to store all tables
    batchTable = cell(1,N);

    for j=0:N-1
            batchTable{j+1} = readtable(['file_' num2str(2*(i+j)) '.csv']);
    end
    
    %Appending all tables in one
    vertcat(batchTable{:})

    %Do batchwise operations below on batchTable
    
    
end

For further information, you can refer to the following documentation pages:

• List folder contents - MATLAB dir (mathworks.com)
• Cell array - MATLAB (mathworks.com)
• Concatenate arrays vertically - MATLAB vertcat (mathworks.com)

[javarocket]

Hi, thank you very much for your help!