how can i plot many series of values in the same plot

i have a series of txt files which i need to use to make one single plot with all of them in it but this command seems not to work properly.

i'm kinda new to matlab so a friend tried to help me out with this one but i don't know how to make it work.

it gives me an error on the first line

%% Import single I-V
clear, clc; close all; % clear variables and cmd window, close figures
% Import raw measurement .epr file
[FileName,FilePath] = uigetfile('*.txt','Choose a measurement');
File = [FilePath, FileName];
data = readmatrix(File,'Range','A1:B70','FileType','delimitedtext');
V = data(:,1);
I = data(:,2);
%% Plot single I-V

figure(1);
plot(V,I,'- .','DisplayName',FileName)
% semilogy(V,abs(I),'- .','DisplayName',FileName)
xlabel('Voltage (V)')
ylabel('Current (mA)')
axis tight
xline(0,'HandleVisibility','off')
yline(0,'HandleVisibility','off')
grid on
box on
legend('Location','northwest','FontSize',8,'Interpreter','None')
pbaspect([1.25 1 1])
%% Import all I-V
% Clear all variables, close all figures, clear command window
clear; close all; clc; 
% Navigate Current Folder to folder containing all files
% Get all .epr files in current directory
txt_files = dir('*.txt');
% Initialise empty cell array to store data
data = cell(0);
% Loop through each csv file to read data from specific rows and columns
for i = 1:numel(txt_files)
    data{i} = readmatrix(txt_files(i).name,'Range','A1:B70','FileType','delimitedtext');
end
%% Plot all I-V 
for i = 1:numel(txt_files)
    V = data{1, i}(:,1);
    I = data{1, i}(:,2);
    figure(1);
    plot(V,I,'- .','DisplayName',txt_files(i).name)
    % semilogy(V,abs(I),'- .','DisplayName',txt_files(i).name)
    hold on
end
hold off
xlabel('Voltage (V)')
ylabel('Current (mA)')
axis tight
%xline(0,'HandleVisibility','off')
%yline(0,'HandleVisibility','off')
grid on
box on
legend('Location','northwest','FontSize',8,'Interpreter','None')
pbaspect([1.25 1 1])

[Star Strider]

What is the error?

It works for me (with an arbitrary file) through ‘figure(1)’. (I don’t have the other files so I didn’t run the rest of it.)

[federico]

i don't know how for other codes like this works but it plots only the selected one, like i said it gives error but i do not see where it can be.

do you happen to have a simpler code since i'm still new to the platform?

ex of code working but only plots one:

clear

%Importare dati, indicare percorso file dati completo

load ST_n_293_testo.txt;

xdata=ST_n_293_testo(:,1); % v (riga, colonna)

ydata=log(ST_n_293_testo(:,2)); % i (riga, colonna)

%plot dati

plot(xdata,ydata,'ro');

title('I-V @ 293K')

xlabel('V [V]');

ylabel('I [mA]');

Answer 1

[Star Strider]

Looking a bit more carefully at your posted code, I believe the problem is that you are creating a new figure in each loop iteration.

Try this instead:

figure(1);

for i = 1:numel(txt_files)

V = data{1, i}(:,1);

I = data{1, i}(:,2);

plot(V,I,'- .','DisplayName',txt_files(i).name)

% semilogy(V,abs(I),'- .','DisplayName',txt_files(i).name)

hold on

end

I could not run the code, so I did not see that before.

.

[federico]

i'll try in a bit, thank you in advance.

I'll keep you updated if u don't mind.

[Star Strider]

My pleasure!

I don’t mind at all!

.

[federico]

i can't seem to be using it right, and i don't know what i'm doing wrong at this point, these are the files i'm currently trying to plot and after this i have to fit them.

i'm totally clueless at this point, considering the fact that i haven't even used matlab before

[Star Strider]

This seems to work correctly here (R2023a).

What do you want your code to do?

% Import raw measurement .epr file
% [FileName,FilePath] = uigetfile('*.txt','Choose a measurement');
Files = dir('*.txt')

Files = 15×1 struct array with fields:
    name
    folder
    date
    bytes
    isdir
    datenum

FileName = Files(1).name

FileName = 'ST_n_100_testo.txt'

File = FileName

File = 'ST_n_100_testo.txt'

% File = [FilePath, FileName];
data = readmatrix(File,'Range','A1:B70','FileType','delimitedtext');
V = data(:,1);
I = data(:,2);
%% Plot single I-V
    
figure(1);
    plot(V,I,'- .','DisplayName',FileName)
    % semilogy(V,abs(I),'- .','DisplayName',FileName)
    xlabel('Voltage (V)')
    ylabel('Current (mA)')
    axis tight
    xline(0,'HandleVisibility','off')
    yline(0,'HandleVisibility','off')
    grid on
    box on
    legend('Location','northwest','FontSize',8,'Interpreter','None')
    pbaspect([1.25 1 1])
%% Import all I-V
% Clear all variables, close all figures, clear command window
clear; close all; clc; 
% Navigate Current Folder to folder containing all files
% Get all .epr files in current directory
txt_files = dir('*.txt');
% Initialise empty cell array to store data
data = cell(0);
% Loop through each csv file to read data from specific rows and columns
for i = 1:numel(txt_files)
    data{i} = readmatrix(txt_files(i).name,'Range','A1:B70','FileType','delimitedtext');
end
%% Plot all I-V 
for i = 1:numel(txt_files)
    V = data{1, i}(:,1);
    I = data{1, i}(:,2);
    figure(1);
        plot(V,I,'- .','DisplayName',txt_files(i).name)
        % semilogy(V,abs(I),'- .','DisplayName',txt_files(i).name)
        hold on
end
hold off
xlabel('Voltage (V)')
ylabel('Current (mA)')
axis tight
%xline(0,'HandleVisibility','off')
%yline(0,'HandleVisibility','off')
grid on
box on
legend('Location','northwest','FontSize',8,'Interpreter','None')
pbaspect([1.25 1 1])

.

[federico]

oh i see the problem was specifing the folder files, since i had to convert them from .ivc to .txt i had both copies in the same folders and mistakes were made while editing blanks spots.

thanks for the patience and the response.

[Star Strider]

As always, (our) pleasure!

Answer 2

[Cris LaPierre]

If you want multiple lines to appear with a single plot command, you need to be plotting a matrix. Each column of data is treated as a series.

X = 1:10;
% 3 columns so 3 lines
Y = rand(10,3);
plot(X,Y)

You can also use multple plot commands combined with a 'hold on'. Without it, each plot command replaces the previous plot.

plot(X,Y(:,1))
hold on
plot(X,Y(:,2))
plot(X,Y(:,3))
hold off

If you haven't done so already, I suggest going through MATLAB Onramp. Ch 9 covers plotting.

[federico]

i'll check this as well, thank you