Read the column 2 and 11 from 45 csv files in 45 subfolder hence plot them.

Hi,

I am using the code below to plot the diatance over U from 45 csv files but as soon as I am running it matlab is crashing.

What I want from the code. is to read all 45 csv files, extract 45 (column 2 and column 11 from the files and plot all in one graph)

Code:

close all; clear all; clc;
projectdir = 'F:\3-PIV_Experimental_Data\Outlet_110\Data_LaserSheet_D\Data_PIV\6-VectorSatistics\PlotOverLine';
files = dir( fullfile(projectdir, '*', '*.csv') );
filenames = fullfile({files.folder}, {files.name});
num_files = length(filenames);
Distance = zeros(num_files,1);
U = zeros(num_files,1);
for i = 1:numel(files);
    filename = filenames{i};
    data = readtable(filename);
    Distance(i) = table2array (data(:,2));
    U(i) = table2array (data(:,11));
end

Plot(Distance,U)

Error:

Unable to perform assignment because the left and right sides have a different number of elements.

Error in BONO1_LSD (line 22)

Distance(i) = table2array (data(:,2));

[Aman Banthia]

Hello,

Can you try removing semi colon at the end of for statement

for i = 1:numel(files)

filename = filenames{i};

data = readtable(filename);

Distance(i) = table2array (data(:,2));

U(i) = table2array (data(:,11));

end

Try to use it like this.

Answer 1

[KSSV]

Save the data into cells. If each file has different dimension.

close all; clear all; clc;
projectdir = 'F:\3-PIV_Experimental_Data\Outlet_110\Data_LaserSheet_D\Data_PIV\6-VectorSatistics\PlotOverLine';
files = dir( fullfile(projectdir, '*', '*.csv') );
filenames = fullfile({files.folder}, {files.name});
num_files = length(filenames);
Distance = cell(num_files,1);
U = cell(num_files,1);
figure
hold on
for i = 1:numel(files);
    filename = filenames{i};
    data = readtable(filename);
    Distance{i} = table2array (data(:,2));
    U{i} = table2array (data(:,11));
    plot(Distance{i},U{i})
end

If the number of rows in each file is same and you know the number of rows.

close all; clear all; clc;
projectdir = 'F:\3-PIV_Experimental_Data\Outlet_110\Data_LaserSheet_D\Data_PIV\6-VectorSatistics\PlotOverLine';
files = dir( fullfile(projectdir, '*', '*.csv') );
filenames = fullfile({files.folder}, {files.name});
num_files = length(filenames);
N = 100 ;  % where N is number of rows in each file 
Distance = zeros(N,num_files);
U = zeros(N,num_files);
for i = 1:numel(files);
    filename = filenames{i};
    data = readtable(filename);
    Distance(:,i) = table2array (data(:,2));
    U(:,i) = table2array (data(:,11));    
end
plot(Distance,U)

[muhammad choudhry]

that works! what if I want to analyze specific files let say file 1 , 13 and 45. what should I do ?

[KSSV]

Pick only those files from filenames by indexing.

Answer 2

[Karim]

Distance(i) = table2array(data(:,2));

Here you are trying to store an entire array into a single placehoder. Unless data(:,2) is a scalar, this wont work.

If the size is the same for all files you can initialize Distance as a matrix:

Distance = zeros(num_files, num_rows_data);

in the loop you need to change the indexing to

Distance(i,:) = table2array(data(:,2));

If the files have different sizes, then you can save the data into a cell array. In this case allocate as

Distance = cell(num_files, 1);

and save data as

Distance{i} = table2array(data(:,2));

Answer 3

[Walter Roberson]

    Distance(i) = table2array (data(:,2));

table2array() of a table with a single numeric variable, is going to produce one row of output for each row in data . You are expecting to store that entire row of output in the single numeric location Distance(i)

I suggest

Distancec = cell(num_files,1);
Uc = cell(num_files,1);
for i = 1:numel(files);
    filename = filenames{i};
    data = readtable(filename);
    Distancec{i} = table2array (data(:,2));
    Uc{i} = table2array (data(:,11));
end

Distance = cell2mat(Distancec);
U = cell2mat(Uc);

plot(Distance, U)

... Except that I suspect you will find that confusing, as there will be no breaks between the files.

Do you want one line per file? If so then try

hold on
cellfun(@(d,u) plot(d,u), Distancec, Uc);
legend(filenames);
hold off
xlim auto; ylim auto