Changing text file name changes the plot of data after using dir('*.txt') ??

new_files = dir('*.txt');

for file = new_files'

    delimiterIn = ' ';
    headerlinesIn = 29;
    A = importdata(file.name,delimiterIn,headerlinesIn);

    % We want to store it into a new 2 column array
    % Changing the Depth from A to microns 

    x1 = A.data(:, 1)/10^4;
    y1 = A.data(:, 2);

    % New array of ion ranges 
    ion_range = [x1 y1];

    % Fitting data to a gaussian
    f = fit(x1,y1,'gauss1');
    h = plot(f, '-');
    set(h, 'LineWidth', 2);

    hold on

end

I have four text files in a folder which I am trying to extract data from, fit the data and plot on the same graph. The text files when titled 40.txt, 80.txt, 160.txt and 250.txt work fine, they result in the expected plot but they do not plot in order meaning the legend on the figure is not in ascending order. So, I read elsewhere that you can change the text file name like so 040.txt, 080.txt, 160.txt and 250.txt, and it will be fixed. But when I do that, the plot of the graph changes and the plots cut off and certain points. Previous to the image shown, when the text files were without the zeros, there were four gaussians plotted.

I cannot work out why this happens - can anyone help?

[Mathieu NOE]

hello

maybe you should share the files so we can better help you

[Megan Powell]

Here are the text files, thanks

Answer 1

[DGM]

Ah. That just happens to work because when the files are renamed, the one with the largest domain gets loaded first.

If they're loaded in natural order, the one with the narrowest domain gets plotted first. Since the way the fit function is plotted without an explicit x input, the subsequent plots are only considered over the domain implied by the current axes extents.

Unless you want to prefetch all the data and find the span of the widest dataset, you can just specify it manually before the first plot:

new_files = dir('*.txt');
for file = new_files'
    delimiterIn = ' ';
    headerlinesIn = 29;
    A = importdata(file.name,delimiterIn,headerlinesIn);
    
    % We want to store it into a new 2 column array
    % Changing the Depth from A to microns 
    x1 = A.data(:, 1)/10^4;
    y1 = A.data(:, 2);
    
    % New array of ion ranges 
    ion_range = [x1 y1];
    
    % Fitting data to a gaussian
    f = fit(x1,y1,'gauss1');
    
    xlim([0 0.5]) % <-- this
    h = plot(f, '-');
    set(h, 'LineWidth', 2);
    hold on
end

[Megan Powell]

Very helpful! Thank you so much :)

Answer 2

[Mathieu NOE]

hello

a "low cost" solution for those who don't have the Curve Fit Toolbox

I force all fitted data to share the same xfit x data - if that may ne of any use / advantage

legend is added , based on file name

all the best

new_files = dir('*.txt');

xmax = 0.5;
xfit = linspace(0,xmax,300);

for ck = 1:numel(new_files)
    filename = new_files(ck).name;
    delimiterIn = ' ';
    headerlinesIn = 29;
    A = importdata(filename,delimiterIn,headerlinesIn);
    
    % We want to store it into a new 2 column array
    % Changing the Depth from A to microns 
    x1 = A.data(:, 1)/10^4;
    y1 = A.data(:, 2);
    
    % New array of ion ranges 
    ion_range = [x1 y1];
    
    % Fitting data to a gaussian
    yfit = my_gauss_fit(x1,y1,xfit);
    
    h = plot(xfit,yfit, '-');
    leg_str{ck} = filename(1:length(filename)-4);
    set(h, 'LineWidth', 2);
    hold on
end

legend(leg_str);
hold off

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function yfit = my_gauss_fit(x,y,xfit)

% Define g(x) = a*exp(-(x-mu)^2/(2*sigma^2)):
g = @(A,X) A(1)*exp(-(X-A(2)).^2/(2*A(3)^2));

%% ---Fit Data: Analitical Strategy---
    % Cut Gaussian bell data
    ymax = max(y); xnew=[]; ynew=[];
    ind = y > 0.1*ymax;
    xnew = x(ind);
    ynew = y(ind);

    % Fitting
    ylog=log(ynew); xlog=xnew; B=polyfit(xlog,ylog,2);

    % Compute Parameters
    sigma=sqrt(-1/(2*B(1))); mu=B(2)*sigma^2; a=exp(B(3)+mu^2/(2*sigma^2)); 

    % Plot fitting curve
    A=[a,mu,sigma];
    yfit = g(A,xfit);

end

[Megan Powell]

Very helpful as my next problem was to remove the .txt from the legend! Thank you

[Mathieu NOE]

My pleasure !