# How to get area under the fit attained by Curve Fitting tool?

2 views (last 30 days)
Anik Mukhopadhyay on 14 Apr 2022
Commented: Sam Chak on 14 Apr 2022
Here I have two data arrays namely t and T. I have used the command
t = linspace(0,270,10)
T = [30 32 34.5 38.6 40 40 42 42.5 42.5 42 41.5]
cftool(t,T)
And the cftool gui to attain the following:
I want to get the area under the curve from (t=0) to (t=180). What should I use in this case. I am a complete novice to MATLAB and I do most of my work using the GUI. If anyone can help me it will be really appreciated.

Alan Stevens on 14 Apr 2022
Try
help trapz

Sam Chak on 14 Apr 2022
You can check if this works:
t = linspace(0, 270, 10);
T = [30 32 34.5 38.6 40 42 42.5 42.5 42 41.5];
% Create a shape-preserving piecewise interpolation from t = 0 to 180
tnew = 0:0.01:180;
pch = interp1 (t, T, tnew, "pchip");
plot(t, T, 'ro', tnew, pch, 'b-', 'linewidth', 1.5)
grid on
xlabel('t')
ylabel('T')
Area_under_blue = trapz(tnew, pch)
Sam Chak on 14 Apr 2022
This is a rough estimation:
Areas of a Triangle plus a Rectangle:
(30 + 42)*150/2 + (180 - 150)*42
ans = 6660

R2022a

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