Creating a fucntion that takes as input multible csv files and converts them into arrays

So i am creating a program for financial analysis, and i want to extend my analysis for more stocks. The following code describes how i input historical data for each company ((:,5) contains close price.). But my analysis has to be done for nearly 70 stocks so doing this 70 times is very time cosnuming. Thus i want to create a fucntion that takes all the csv files as inputs and gives back the final arrays with the closing prices. My initial idea was the following but it does not seem to work and i don't know how to make a fuction with variable inputs and outputs!

Thanks in advance!

%Apple
AAPL1=readtable('AAPL.csv');
Close=AAPL1(:,5);
AAPL=table2array(Close);
%Adobe
ADBE1=readtable('ADBE.csv');
Close=ADBE1(:,5);
ADBE=table2array(Close);
%Applied Materials
AMAT1=readtable('AMAT.csv');
Close=AMAT1(:,5);
AMAT=table2array(Close);
%Advanced Micro Devices
AMD1=readtable('AMD.csv');
Close=AMD1(:,5);
AMD=table2array(Close);

%Fucntion
function [Array] = ConvertTablesToArrays(Table)
 
    Table1=readtable(Table)
    Close=Table1(:,5);
    Array=table2array(Close)
    
    
end

[Stephen23]

One of the main problems with your approach is that you have forced meta-data into variable names. While this is easy to do by hand, it makes any kind of loop over those variables slow, complex, liable to bugs, and difficult to debug:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Instead of forcing meta-data into variable names, you should note that meta-data is data, and data should be stored in variables (not in variable names). For example your code would be simpler and much more efficient using indexing and simple cell arrays or numeric arrays. Then writing your loop will also be much simpler.

Answer 1

[bharath pro]

D = 'path_to_folder';
S = dir(fullfile(D,'*.xlsx')); 
for k = 1:numel(S)
  F = fullfile(D,S(k).name);
  [S(k).num,S(k).txt,S(k).raw] = csvread(F); 

This line stores all csv files data in a directory to the variable S. You can then access the data of each sheet by looping and getting S(i).num form which you can get the desired values.

[Spyridon Kariofylis]

I am using matlab online, so everything is stored in matlab drive. How to i declare that as path?

[bharath pro]

You can import the files to matlab drive and copy the path of the files from there

[Spyridon Kariofylis]

D = '/MATLAB Drive/ErgasiaCAPM';
S = dir(fullfile(D,'*.csv')); 
for k = 1:numel(S)
  F = fullfile(D,S(k).name);
  [S(k).num,S(k).txt,S(k).raw] = csvread(F); 
end

So i used this and this error came by : Error using csvread

Too many output arguments.

Then i tried to open one csv file with csvread like that

csvread("AAPL.csv")

and found another error

Mismatch between file and format character vector.

Trouble reading 'Numeric' field from file (row number 1, field number 1) ==> Date,Open,High,Low,Close,Adj Close,Volume\n

Error in csvread (line 48)

m=dlmread(filename, ',', r, c);

[bharath pro]

Can you try readmatrix command instead of csvread command.

[Spyridon Kariofylis]

Same error appears

Error using readmatrix

Too many output arguments.

[Stephen23]

This answer and the comments above mix up different functions.

The function xlsread has three outputs, corresponding to numeric, text, and raw data.

The functions csvread and readmatrix only have one output.

Swapping csvread for readmatrix will not fix an incorrect number of output arguments.

[Spyridon Kariofylis]

I came up with another approach but i still cant figure it out.

files = dir('*.csv');

With this line of code i have a 66x1 struct.

files.name

in names all my stock indexes are stored ( 'AAPL.csv' , 'ACN.csv') and so on.

Now i must loop in each one files.name and for each, i must extract column 5 ((:,5)) and store all closing prices in one matrix.

(Files are from yahoo finanace , typical historical prices format containing date. open, high low etc.)