How to fix the precession difference error of variables in matlab?

I have 2 data sets named T and T2 as shown in the below figure with values ranging with a precession of 1e-5.

The expected max difference of T1-T2 should appear at Sample number 20 through visual inspection from figure 1. However, when I plot T1-T2 in matlab, I get completely a wrong plot as shown below with sample number 44 as maximum of difference, which is not true. In this regard, could some one help me to solve this issue.

[Dyuman Joshi]

Can you attach your data?

[Kalasagarreddi Kottakota]

Hi, I attach the data of T1,T2 and T1-T2.

Answer 1

[Dyuman Joshi]

If you look at the values, you will get an idea as to why that's happening -

format long
T1=load('T1.mat').T1;
T2=load('T2.mat').T2;
T1(20)

ans = 
     5.116663670052163e-07

T2(20)

ans = 
     1.247071549704016e-10

T1(20)-T2(20)

ans = 
     5.115416598502459e-07

T1(44)

ans = 
     6.325269098750142e-06

T2(44)

ans = 
     5.813727438899893e-06

T1(44)-T2(44)

ans = 
     5.115416598502488e-07

As the values increase, on graph it may look like the difference is smaller but that is compared to the original values (absolute scale). If you want to get a clear idea, compare on an relative scale.

%comparing to T1
plot(1:numel(T1),(T1-T2)./T1)

%comparing to T2
plot(1:numel(T1),(T1-T2)./T2)

Now you can see the spike is near 20, as you observed

Answer 2

[Abderrahim. B]

You are replying on what your eyes see, use max function.

clear 
close all
load(websave("T1", "https://www.mathworks.com/matlabcentral/answers/uploaded_files/1105360/T1.mat"))
load(websave("T2", "https://www.mathworks.com/matlabcentral/answers/uploaded_files/1105365/T2.mat"))

figure 

subplot(2,1,1)
plot(T1)
hold on
plot(T2)
subplot(2,1,2)
plot(T1 - T2)

[maxV idx] = max(T1 -T2) % the plot is correct

maxV = 5.1154e-07

idx = 44