How to extract data selection from multiple .txt files and plot one graph?

Question

Leandro 2024-4-16

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2107531-how-to-extract-data-selection-from-multiple-txt-files-and-plot-one-graph

评论： Cris LaPierre 2024-4-17

采纳的回答： Cris LaPierre

Sample Potentiostatic EIS.txt

在 MATLAB Online 中打开

Hello everyone,

I have multiple .txt files like the one (please, check the .txt file enclosed). The data of interest is these two specific columns "Zreal" and "Zimag" (it can be seen in the image below):

I've created to scripts. One named 'read_gamry_data' and the other 'nyquist_gamry'.

Here is the code 'read_gamry_data'

% EDIT: adding function call so errors are displayed here (CL)
data = read_gamry_data('Sample Potentiostatic EIS.txt')
data =

  0x1 empty cell array
function [data] = read_gamry_data(fname)
%READ_GAMRY_DATA Gets the data matrices in the file "fname" and
%stores them into the cell "data"
%get all lines of the file
stra = {};
fid=fopen(fname,'r');
sl = fgetl(fid);
while ischar(sl)
    stra{end+1,1}=strtrim(sl);
    sl = fgetl(fid);
end
fclose(fid);
%get the EIS data from the gamry .txt files
strid_dataset = 'ZCURVE';
id_start = [];
data = cell(length(id_start),1);
for y = 1:length(id_start)
    for z = id_start(y):id_end(y)
        if strcmp(strid_dataset,stra{z}(1:min(length(stra{z}),length(strid_dataset))))
            %read data matrix
            rstart = z+3;
            rend = rstart;
            while rend<=id_end(y) && length(split(stra{rend}))>1
                rend = rend+1;
            end
            rend = rend-1;
            break;    
        end
    end
    data{y}=zeros(rend-rstart+1,length(split(stra{rstart})));
    for z = rstart:rend
        data{y}(z-rstart+1,:)=(sscanf(stra{z},'%f'))';
    end
end
end % added this CL

and here is the code of 'nyquist_gamry' script. Before just plotting, I need to correct the data by the area, so I tried:

clear all;close all;

dir_files = 'EIS'

area = (pi/4)*1.5^2

fname = dir(fullfile(dir_files,'*.txt'));

for a = 1:length(fname)

data{a} = read_gamry_data(strcat(dir_files,'/', fname{a}));

data{a}{1}(:,1:2) = area.*data{a}{1}(:,1:2);

plotgraph(1,data{a}{1}(:,1),-data{a}{1}(:,2))

hold on

end

xlabel('Z_{real}(\Omega.cm^2)', 'FontSize', 12)

ylabel('-Z_{imag}(\Omega.cm^2)','FontSize', 12)

set(gca,"dataaspectratio",[1,1,1])

I constantly having errors, especially saying that my index is not supported. Can anyone try to run it and see if you can help me with? I would like to hear any suggestion from you all.

Kindly

Leandro

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Cris LaPierre 2024-4-16

编辑：Cris LaPierre 2024-4-16

I edited your code so that it could be run here. The sample file does not generate any errors, but the final result is also empty, so yout code is not properly loading the data..

Please share the full error message (all the red text).

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Answer 1

Cris LaPierre 2024-4-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2107531-how-to-extract-data-selection-from-multiple-txt-files-and-plot-one-graph#answer_1442381

在 MATLAB Online 中打开

Sample Potentiostatic EIS.txt

The indexing error suggests something is wrong with how your code handles multiple files. As for loading the data, if your files all share the exact same formatting, you can just use readtable.

data = readtable('Sample Potentiostatic EIS.txt','numHeaderLines',96)

data = 81x11 table

Pt Time Freq Zreal Zimag Zsig Zmod Zphz Idc Vdc IERange __ ____ __________ ______ ________ ____ ______ _________ ___________ _________ _______ 0 7 1.0001e+06 198.38 -0.30052 1 198.38 -0.086796 9.714e-07 -0.000675 9 1 8 7.9439e+05 199.27 0.44131 1 199.27 0.12689 -5.0535e-07 -0.000702 9 2 10 6.3098e+05 199.49 0.85197 1 199.5 0.24469 1.8085e-06 -0.000656 9 3 11 5.0123e+05 199.52 0.8388 1 199.52 0.24088 7.9994e-07 -0.000629 9 4 12 3.9811e+05 199.5 0.64289 1 199.5 0.18463 -3.8204e-07 -0.00063 9 5 14 3.1627e+05 199.5 0.34671 1 199.5 0.099577 2.9806e-07 -0.000603 9 6 15 2.512e+05 199.7 0.097624 1 199.7 0.028009 4.0072e-06 -0.000576 9 7 16 1.9955e+05 199.63 -0.17299 1 199.63 -0.049651 1.8076e-07 -0.000565 9 8 17 1.5842e+05 199.52 -0.57837 1 199.52 -0.16609 5.2998e-07 -0.00053 9 9 19 1.2595e+05 199.43 -0.93185 1 199.43 -0.26771 9.6905e-07 -0.000514 9 10 20 99978 199.52 -1.0675 1 199.53 -0.30655 4.8914e-07 -0.00048 9 11 21 79453 199.44 -1.707 1 199.44 -0.49038 1.132e-06 -0.000485 9 12 23 63078 199.49 -2.2827 1 199.51 -0.65557 4.9528e-07 -0.000492 9 13 24 50103 199.51 -3.1223 1 199.53 -0.89659 4.9509e-07 -0.000495 9 14 25 39811 199.48 -3.9843 1 199.52 -1.1442 5.1864e-07 -0.000489 9 15 27 31609 199.51 -5.0752 1 199.57 -1.4572 5.1111e-07 -0.000495 9

plot(data.Zreal,-data.Zimag)

xlabel('Z_{real}(\Omega.cm^2)', 'FontSize', 12)

ylabel('-Z_{imag}(\Omega.cm^2)','FontSize', 12)

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Cris LaPierre 2024-4-17

在 MATLAB Online 中打开

The issue is that fname is a structure, not a cell array.

Another issue is that the number format is not consistant between your files. Specifically, the decimal separator is a period in the first file you shared, but a comma in the second one. Once that is consistant, the error below goes away. Since a period is the default one, the code below shows how to use readtable to load a file with a comma as the separator.

It's a bit more, but I load the file first as text, find the ZCURVE TABLE row, then use that as an input to readtable to set the number of headerlines.

fname = dir('*.txt')
fname = 2x1 struct array with fields:
    name
    folder
    date
    bytes
    isdir
    datenum

You can access the EIS folder as you currently do, but I would update the input to the read function to use fullfile based on the results of dir.

area = (pi/4)*1.5^2;

for a = 1:length(fname)

str = readlines(fullfile(fname(a).folder, fname(a).name));

idx = find(str=="ZCURVE TABLE");

data{a} = readtable(fullfile(fname(a).folder, fname(a).name),'numHeaderLines',idx,"DecimalSeparator",",");

data{a}(:,["Zreal","Zimag"]) = area.*data{a}(:,["Zreal","Zimag"]);

plot(data{a}.Zreal,-data{a}.Zimag)

hold on

end

Error using .* (line 36)
Applying the function 'times' to the variable 'Zreal' generated an error.

Caused by:
Undefined function 'times' for input arguments of type 'cell'.

hold off

xlabel('Z_{real}(\Omega.cm^2)', 'FontSize', 12)

ylabel('-Z_{imag}(\Omega.cm^2)','FontSize', 12)

Leandro 2024-4-17

Now it is working! Thanks for your time.

Do you mind if I ask how would you update this specifically? I couldnt get what you said here: "update the input to the read function to use fullfile based on the results of dir"

It would be helpful if I can separate it in folders per batch of samples.

Kindly