How to store values from a loop?

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

[Stephen23]

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

Answer 1

[Sanskar]

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

Answer 2

[Aman]

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

The average of each iteration is stored in the V_favg_all array.

Hope this Helps!

Answer 3

[Naman]

Hi Edward,

Here you are overriding the V_favg value with every iteration of for loop

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

Instead create an array V_favg initially outside the for loop.

% Declaring V_favg2 vector outside the for loop.

V_favg = zeros(1,numCPs) ;

and keep storing average of V_f in it with each iteration of for loop.

% saving the average value of V_f from each iteration into V_favg array

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

Hope it will help you.