How to store values from a loop?

Question

Edward Apraku 2023-6-14

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1982649-how-to-store-values-from-a-loop

回答： Naman 2023-6-14

I have a code that loops through multiple DTA text files and graphs them together. I want to save the average value of V_f from each iteration but am currently stuck becuase it keeps overwriting and only saves the average V_f from the last DTA file.

clear all; clc; close all; 
[filename,pathname]=uigetfile('*.DTA','MultiSelect','on');
numCPs=length(filename);
if numCPs>10
    numCPs=1;
end
figure
ax=axes;
ax.Box='on';
ax.LineWidth=1.5;
ax.XAxis.FontSize=20; ax.XLabel.FontSize=20;
ax.YAxis.FontSize=20; ax.YLabel.FontSize=20;
hold on
for count=1:1:numCPs
    if numCPs>1
        CPdata=importdata(fullfile(pathname,filename{count}),' ');
    else
        CPdata=importdata(fullfile(pathname,filename),' ');
    end
       temp=strsplit(CPdata{15});
       endIndex=length(CPdata);
    for i=1:length(CPdata)
        temp=strsplit(CPdata{i});
        if temp{1}=="CURVE"
            startIndex=i+3;
        end
        endIndex=i-1;
    end
        data=[];
    for i=startIndex:endIndex
        temp=strsplit(CPdata{i});
        data=[data;str2num(temp{3}),str2num(temp{4})];
    end
    Time=data(:,1); %time
    V_f=data(:,2); %ohm
    V_favg=mean(data(:,2));
    
    if numCPs>1
        plot(Time,V_f,'-o','MarkerSize',2,'LineWidth',3,'DisplayName',filename{count});
    else
        plot(Time,V_f,'-o','MarkerSize',2,'LineWidth',3,'DisplayName',filename);
    end
    xlabel("Time (s)"); ylabel("V_f (V vs. Ref.)");
end
legend('AutoUpdate','off');
axis square;
axis([0 7200 0 10])
hold off

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Stephen23 2023-6-14

在 MATLAB Online 中打开

Note that you can replace this fragile code:

numCPs=length(filename);
if numCPs>10
    numCPs=1;
end
..
for count=1:1:numCPs
    if numCPs>1
        CPdata=importdata(fullfile(pathname,filename{count}),' ');
    else
        CPdata=importdata(fullfile(pathname,filename),' ');
    end
    ..
end

with this simpler and much more robust code:

filename = cellstr(filename);
..
for count = 1:numel(filename)
    CPdata = importdata(fullfile(pathname,filename{count}),' ');
    ..
end

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Answer 1

Sanskar 2023-6-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1982649-how-to-store-values-from-a-loop#answer_1255269

在 MATLAB Online 中打开

From your question I got that you want to get all the average value but it overwrites the previous one.

Since, in the following line you are updating the V_favg in every iteration so it overwrites.

V_favg=mean(data(:,2));

To store the average value, you can create an empty 1-D array, before you start the loop and you can append the average value from every iteration to that array.

 ....
ax.LineWidth=1.5;
ax.XAxis.FontSize=20; ax.XLabel.FontSize=20;
ax.YAxis.FontSize=20; ax.YLabel.FontSize=20;
hold on
V_favg = []; % initialize empty array
for count = 1:1:numCPs
    ...
    ...
     Time=data(:,1); %time
    V_f=data(:,2); %ohm
    V_favg(end+1)=mean(data(:,2)); %Appending to initialized array
     if numCPs>1
        plot(Time,V_f,'-o','MarkerSize',2,'LineWidth',3,'DisplayName',filename{count});
    else
        plot(Time,V_f,'-o','MarkerSize',2,'LineWidth',3,'DisplayName',filename);
    end
    xlabel("Time (s)"); ylabel("V_f (V vs. Ref.)");
    ...
    ...
end

Happy to help you,

Sanskar

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Answer 2

Aman 2023-6-14

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1982649-how-to-store-values-from-a-loop#answer_1255264

在 MATLAB Online 中打开

Hi Edward,

To save the average V_f value from each DTA file, you can create an array V_favg_all to store the average values.

Here's an updated version of your code that includes this modification:

clear all; clc; close all; 
[filename,pathname]=uigetfile('*.DTA','MultiSelect','on');
numCPs=length(filename);
if numCPs>10
    numCPs=1;
end
figure
ax=axes;
ax.Box='on';
ax.LineWidth=1.5;
ax.XAxis.FontSize=20; ax.XLabel.FontSize=20;
ax.YAxis.FontSize=20; ax.YLabel.FontSize=20;
hold on
V_favg_all = []; % initialize array to store average V_f values
for count=1:1:numCPs
    if numCPs>1
        CPdata=importdata(fullfile(pathname,filename{count}),' ');
    else
        CPdata=importdata(fullfile(pathname,filename),' ');
    end
       temp=strsplit(CPdata{15});
       endIndex=length(CPdata);
    for i=1:length(CPdata)
        temp=strsplit(CPdata{i});
        if temp{1}=="CURVE"
            startIndex=i+3;
        end
        endIndex=i-1;
    end
        data=[];
    for i=startIndex:endIndex
        temp=strsplit(CPdata{i});
        data=[data;str2num(temp{3}),str2num(temp{4})];
    end
    Time=data(:,1); %time
    V_f=data(:,2); %ohm
    V_favg=mean(data(:,2));
    
    V_favg_all = [V_favg_all V_favg]; % append the new V_favg to the end of the V_favg_all array
    if numCPs>1
        plot(Time,V_f,'-o','MarkerSize',2,'LineWidth',3,'DisplayName',filename{count});
    else
        plot(Time,V_f,'-o','MarkerSize',2,'LineWidth',3,'DisplayName',filename);
    end
    xlabel("Time (s)"); ylabel("V_f (V vs. Ref.)");
end
legend('AutoUpdate','off');
axis square;
axis([0 7200 0 10])
hold off