Question

I’ve performed some cycle tests of steel joints. The tests conditions include the application of 3 cycles per amplitude value and three different amplitudes were used.

Now I have a huge text file with rotation and moment values but I need to determine the stiffness of each branch of the diagram with a regression analysis method. Therefore I need to separate each cycle.

Do you recommend

• Mathematica,
• Matlab,
• Excel,
• or other program best suited to make this task easier?

Many thanks as always for your advice.

Answer 1

It’s not entirely clear what you’re looking for in the question. I also don’t know much about Mathematica or Excel, but I’ll say as much as I can about how Matlab might be used to address this problem.

When you say ‘separate each cycle’, I assume you mean that your text file contains data about all 3 cycles and you want to partition it into 3 separate datasets regarding each individual cycle. I would guess that Matlab will import your data file (the file->import data menu is quite flexible, and I’ve used it successfully with e.g. 30MB files, but if your files are hundreds of MB that might be a problem).

Assuming there is some structure to the data file, I would expect that you can slice it to achieve your desired partition, e.g.

cycle1 = data(1:3:end, :); %If data from cycles are stored in alternate rows
cycle1 = data(1:end/3, :); %If data from cycles are stored in blocks of rows
cycle1 = data(:, 3);       %If data from cycles are stored in separate columns

etc. If you comment with a description of structure of the file I may be able to help further.

Regarding regression analysis, Matlab has several tools; polyfit is quite flexible and might satisfy your requirements. I don’t know anything about materials, but I may be able to give better suggestions if you explain the relationship between stiffness and the measures variables.