Making loop for a function 'xlsread'

Hi,

I have many files

1.csv, 2.csv, 3.csv.................................39.csv

How can I make a simple loop to convert them all together.

I simply want to obtain

data1=xlsread('1.csv');
data2=xlsread('2.csv');
data3=xlsread('3.csv');
.
.
.
.
data39=xlsread('39.csv');

I have tried to make its loop but I am getting stuck.

q = dir('Data/*.csv');
filenames = {q.name};
nfiles = length(filenames);

for i=1:nfiles
    thisfile=filenames{i};
    
end

Kindly if someone can assist.

regards

[Stephen23]

Use a DataStore:

https://www.mathworks.com/help/matlab/ref/matlab.io.datastore.spreadsheetdatastore.html

"I simply want to obtain"

Numbering lots of variable names like that is one way that beginners force themselves into writing slow, complex, inefficient, obfuscated, buggy code that is hard to debug. Best avoided.

The MATLAB approach is to use indexing. Indexing is simple and efficient, unlike what you are trying to do.

Answer 1

[Dyuman Joshi]

Use readmatrix instead of the deprecated xlsread().

q = dir('Data/*.csv');
nfiles = numel(filenames);

for k=1:nfiles
    %file name
    str = fullfile(q(k).folder, q(k).name)
    %read the data
    arr=readmatrix(str);
    
    
    %perform necessary/required operations on the data
    
end

You can also preallocate a numeric array or a cell array to store the data - Preallocation

Also, since you have files named sequentially, you can read them accordingly as in the 1st example here -https://in.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

(Note that the method you have used is also mentioned in the documentation linked)

[Abdul Hannan Qureshi]

Thanks for guideline. I have seen the example and it was helpful.

q = dir('Data/*.csv');
filenames = {q.name};
nfiles = numel(filenames);

for k=1:nfiles
    mydata{k} = readtable(q(k).name); 
end

I followed this, but seems like 'mydata' is storing all files data inside as one. How can I import each file as seperate.

[Chuguang Pan]

@Abdul Hannan Qureshi you can extract each file from mydata cell array seperately.

[Stephen23]

"How can I import each file as seperate."

They already are: every cell of MYDATA contains a separate array imported from your files. You can trivially process those arrays using e.g. a loop and indexing. For example, the 2nd file's data: MYDATA{2}. So easy.

In contrast your approach of having lots and lots and lots of numbered variables is going to force you into writing slow, complex, inefficient code (either by doing lots of copy-and-pasting or by dynamically accessing the variable names... either way is a waste of time). Best avoided.

[Abdul Hannan Qureshi]

Thanks @Stephen23 @Chuguang Pan and @Dyuman Joshi for guidance and assistance.

Answer 2

[Chuguang Pan]

xlsread is not recommended, you can use readtable/readmatrix/readcell depend on what type of data you want to read.

The following code may be helpful:

q = dir('Data/*.csv');
filenames = {q.name};
Datas=cell(numel(filenames),1);
for i=1:length(filenames)
    Datas{i}=readtable(filenames(i));
end

[Dyuman Joshi]

Datas=cell(39,1);

Hard coding values is not optimal.

Use numel() or size().