Trying to find the slope from the graph regenerate in MATLAB and then find a 0.2% offset

The picture below was generate from the following script. The data comes from a computer regenerate data.

clc;

clear all;

Information6 = xlsread('/SteelTest1.is_tens_RawData/Specimen_RawData_1.xlsx', 'A:E');

length_All = length(Information6);

Information6_modifiy = Information6(3:length_All,:);

figure

plot(Information6_modifiy(:,5), Information6_modifiy(:,4), '-.g', 'LineWidth', 2);

hold all

title('Steel', 'FontSize', 25)

xlabel('Strain (mm/mm)', 'FontSize', 20), ylabel ('Stress (MPa)','FontSize', 20);

legend({'Steel Test 1', 'Steel Test 2', 'Steel Test 3'}, 'FontSize', 15, 'Location', 'Northwest');

set(gca, 'LineWidth', 1,'FontSize', 15,'XminorTick','on','YMinorTick','on');

axis square;

Now how would you go about finding the slope and then finding a 0.2% offset. I attempted different options but none of them close to finding the slope of this graph and drawing a 0.2% offset based on the slope

Thanks for your help,

A real novice with MatLab

[Walter Roberson]

The slope of what part of the graph?

0.2% offset relative to what? Are you asking for the 99.8% confidence interval?

[CR]

Sorry, I am trying to find a slope on the line left side. It is starting at about (0,0) and going up to about (0.025, 800). Basically, I need to find the modulus of elasticity or Young's modulus of this particular metal. I can do the calculation but I simply don't know how to program Matlab to find the slope and draw the 0.2% offset yield or young's modulus.

Thank you.

Answer 1

[Star Strider]

I don’t have your data, but I would calculate it as:

x = [0.002; 0.022];             % From Plot
y = [10;  720];                 % From Plot
C = [ones(size(x)) x]\y;
Slope = C(2)

Slope =
    35.5000e+003