Please anyone help me to plot the graph(load against extension) from the raw data(excel) and calculate the area under the graph of it?

i want to plot the graph that i imported from the excel and calculate the area under the curve

Answer 1

[Star Strider]

This should work:

[D,S] = xlsread('Al 1.csv');
Ext = D(:,2);
Load = D(:,3);

AUC = cumtrapz(Ext, Load);                                  % Area Under Curve (Cumulative Integral)

figure(1)
plot(Ext, Load)
hold on
plot(Ext, AUC)
hold off
grid
xlabel('Extension (mm)')
ylabel('Load (kN)')
legend('Data', 'Cumulative Area Under Curve (kN\cdotmm)', 'Location','NW')
text(5, 25, sprintf('Total Area Under Curve = %.3f kN\\cdotmm', AUC(end)))

[Matzulk]

thanks it works, I also check with another statistical software NCSS and Minitab

[Star Strider]

My pleasure.

I can only help with MATLAB. I do not have NCSS or Minitab.

[Matzulk]

what about the data have negative values?

[Star Strider]

There are no negative values in the data you attached. I do not know what data you are analysing, so you would have to determine how to handle any negative data. In my code, they would be integrated along with the positive data.

For example, if you wanted to set all negative ‘Load’ data to zero, you would add this line:

Load(Load < 0) = 0;

[Matzulk]

Sorry I forgot to attach the file

[Star Strider]

Before I start to work with your ‘PVC 2.csv’ file, what do you want to do with the negative values? I need to know so I can write the code correctly.

[Matzulk]

i need to plot the graph load against extension. raw data for load contain negative values

[Star Strider]

My code works with negative as well as positive values:

<<www-mathworks-com-matlabcentral-answers-uploaded_files-51908-Please-20anyone-20help-20me-20to-20plot-20the-20graph-load-20against-20extension--20from-20the-20raw-20data-excel--20and-20calculate-20the-20area-20under-20the-20graph-20of-20it-20--202016-2002-2010.png>>

[Matzulk]

so where do i get the area under the curve for this graph?thank you

[Star Strider]

I updated the code to print the total area under the curve in a text object, now placing it so that its position automatically scales to the axis limits:

[D,S] = xlsread('PVC 2.csv');
Ext = D(:,2);
Load = D(:,3);

AUC = cumtrapz(Ext, Load);                                  % Area Under Curve (Cumulative Integral)

figure(1)
plot(Ext, Load)
hold on
plot(Ext, AUC)
hold off
grid
xlabel('Extension (mm)')
ylabel('Load (kN)')
legend('Data', 'Cumulative Area Under Curve (kN\cdotmm)', 'Location','NW')
txtx = min(xlim) + 0.05*diff(xlim);
txty = min(ylim) + 0.05*diff(ylim);
text(txtx, txty, sprintf('Total Area Under Curve = %.3f kN\\cdotmm', AUC(end)))

<<www-mathworks-com-matlabcentral-answers-uploaded_files-51923-Please-20anyone-20help-20me-20to-20plot-20the-20graph-load-20against-20extension--20from-20the-20raw-20data-excel--20and-20calculate-20the-20area-20under-20the-20graph-20of-20it-20--202016-2002-2010.png>>

[Matzulk]

Once again it works.Thank you sir.

[Star Strider]

As always, my pleasure.