Problem using polyfit with NaN data
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Trying to find Young's Modulus in a specific range. I was to plot the the data for that range, but when I try to get the slope value, it gives me NaN. I worked on the code for days and tried various methods and loopholes, but I can't seem to get it.
data = readtable('TITLE.txt','ReadVariableNames',true);
Load = data.Load(1:end);
Displacement = data.Displacement(1:end);
Strain = data.Strain(1:end);
Strain(Strain < 0.001) = NaN;
plot(Strain)
Strain(Strain > 0.003) = NaN;
plot(Strain)
p = plot(Strain, Load, '.', 'color','r')
title('Youngs Modulus','FontSize', 20);
xlabel('Strain (in/in)', 'FontSize', 15);
ylabel('Load(lbf)', 'FontSize', 15);
polyfit(Strain, Load, 1)
polyval(Strain, Load)
采纳的回答
To avoid having NaN in polyfit I would use
iFit = isfinite(Strain)
c = polyfit(Strain(iFit),Load(iFit))
% ok to have NaN when calculating fitted Load
yfit = polyval(c,Strain)
By the way shouldn't Young's Moduls use Tensile Stress (Load/Area) rather than just raw load?
5 个评论
Jade Pearson
2020-11-18
编辑：Jade Pearson
2020-11-18
Jon
2020-11-18
Sorry, for the typo. If this solves your problem when you get a chance please accept the answer so others who might have a similar issue will know an answer is available
Jon
2020-11-18
Thanks - One last style point for the future, the MATLAB answers site encourages brief titles for questions with just the essense of the problem, e.g. Problem using polyfit with NaN data, and then putting the details into the body of the question. Not a big thing but it makes it a little easier to look through the questions if they have brief titles.
Jade Pearson
2020-11-18
Jon
2020-11-18
Very nice - I didn't realize you could edit the original question title. Looks very clean now!
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