How to find value on the graph

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Offroad Jeep
Offroad Jeep on 17 Oct 2018
Edited: KALYAN ACHARJYA on 17 Oct 2018
Hi To All, the following values plot a hysteresis graph. I want to check what is the value of Mag_Field for Magnetization = 0 on positive x and negative x axes..... Regards
B=[1 0.9286 0.8571 0.7857 0.7143 0.6429 0.5714 0.5 0.4286 0.3571 0.2857 0.2143 0.1429 0.0714 0 -0.0714 -0.1429 -0.2143 -0.2857 -0.3571 -0.4286 -0.5 -0.5714 -0.6429 -0.7143 -0.7857 -0.8571 -0.9286 -1 -0.9286 -0.8571 -0.7857 -0.7143 -0.6429 -0.5714 -0.5 -0.4286 -0.3571 -0.2857 -0.2143 -0.1429 -0.0714 0 0.0714 0.1429 0.2143 0.2857 0.3571 0.4286 0.5 0.5714 0.6429 0.7143 0.7857 0.8571 0.9286 1]
B=B'
M = [0.988 0.9993 0.9971 0.9912 0.9918 0.9852 0.9777 0.9697 0.9604 0.9476 0.9229 0.9206 0.883 0.8488 0.8 0.74 0.609 0.4753 0.2868 -0.0352 -0.3133 -0.6251 -0.8118 -0.9346 -0.9835 -0.999 -0.9988 -0.9937 -0.9935 -0.9922 -0.9912 -0.9917 -0.9911 -0.9844 -0.9762 -0.9708 -0.9621 -0.9531 -0.9432 -0.9422 -0.9251 -0.8979 -0.8578 -0.7911 -0.7061 -0.5588 -0.359 -0.1184 0.2288 0.5402 0.7588 0.8951 0.9752 0.9977 0.9991 0.9949 0.9923 ]
M = M'
Mag_Field = B
Magnetization = M
plot(Mag_Field, Magnetization, 'r--*')
xlabel('Magnetic Field B')
ylabel('Magnetization')
grid on

Answers (2)

KALYAN ACHARJYA
KALYAN ACHARJYA on 17 Oct 2018
Edited: KALYAN ACHARJYA on 17 Oct 2018
B=[1 0.9286 0.8571 0.7857 0.7143 0.6429 0.5714 0.5 0.4286 0.3571 0.2857 0.2143 0.1429 0.0714 0 -0.0714 -0.1429 -0.2143 -0.2857 -0.3571 -0.4286 -0.5 -0.5714 -0.6429 -0.7143 -0.7857 -0.8571 -0.9286 -1 -0.9286 -0.8571 -0.7857 -0.7143 -0.6429 -0.5714 -0.5 -0.4286 -0.3571 -0.2857 -0.2143 -0.1429 -0.0714 0 0.0714 0.1429 0.2143 0.2857 0.3571 0.4286 0.5 0.5714 0.6429 0.7143 0.7857 0.8571 0.9286 1];
Mag_Field=B';
M=[0.988 0.9993 0.9971 0.9912 0.9918 0.9852 0.9777 0.9697 0.9604 0.9476 0.9229 0.9206 0.883 0.8488 0.8 0.74 0.609 0.4753 0.2868 -0.0352 -0.3133 -0.6251 -0.8118 -0.9346 -0.9835 -0.999 -0.9988 -0.9937 -0.9935 -0.9922 -0.9912 -0.9917 -0.9911 -0.9844 -0.9762 -0.9708 -0.9621 -0.9531 -0.9432 -0.9422 -0.9251 -0.8979 -0.8578 -0.7911 -0.7061 -0.5588 -0.359 -0.1184 0.2288 0.5402 0.7588 0.8951 0.9752 0.9977 0.9991 0.9949 0.9923];
Magnetization=M';
plot(Mag_Field,Magnetization,'r--*');
xlabel('Magnetic Field B');
ylabel('Magnetization');
grid on;
%Magnetization=cell2mat(Magnetization);
idx1=find(Magnetization<=0, 1,'last');
%idx=find(Magnetization==0.9852);
idx2=knnsearch(Magnetization,0);
%idx2=find(Magnetization<0, 1,'last');
fprintf('The Magnetic Field value is %.4f in +ve axis',Mag_Field(idx1));
idx=find(Magnetization>=0, 1,'last');
fprintf('\nThe Magnetic Field value is %.4f in -ve axis',Mag_Field(idx2));
Command Window
The Magnetic Field value is 0.3571 in +ve axis
The Magnetic Field value is -0.3571 in -ve axis>>
Both value exist in B array.

dpb
dpb on 17 Oct 2018
Alternatively to just finding point in the dataset..
ix=find(abs(B)==1); % find the breakpoint locations in the B vector
for i=1:2 % for the two sections
B0(i)=interp1(M(ix(i):ix(i+1)),B(ix(i):ix(i+1)),0); % find linear interpolated crossing
end
>> B0 % See what answers are...
B0 =
-0.3493 0.3815
>>

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