Intercept of each line to y-line

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Sarfaraz Ahmed
Sarfaraz Ahmed 2022-2-20
编辑： DGM 2022-2-20
Hello folks,
I am making curve fit plot for some data and trying to make intercept point of each data line with y-line.
For examples. each line should give intercept point so there will be 10 intercept points which can be stored in any array.
I am concerning only x-axis value in the x-yline(1.5228, '--') intercept values. I tried with intercept commands but the problem is here I am dealing with objects.
I am share here code. please have a look and help in this regard, so that when I run a code it will provides x-y intercept values.
clear
close all
Data=[
0.11 0.3 0.28 0.6 0.31
0.23 0.78 0.57 1.08 0.43
0.26 0.95 0.84 1.25 0.46
0.55 1.2 1.1 1.5 0.75
6.95 7.05 8.25 7.35 7.15
5.2 4.34 4.68 4.64 5.4
4.81 4.74 4.21 5.04 5.01
3.96 4.07 3.96 4.37 4.16
3.88 3.78 3.25 4.08 4.08
2.69 2.4 2.81 2.7 2.89
2.36 2.35 2.7 2.65 2.56
2.24 2.28 2.35 2.58 2.44
1.9 2.07 1.94 2.37 2.1
1.7 1.95 1.68 2.25 1.9
0.57 1.67 1.47 1.97 0.77
0.47 0.89 1.1 1.19 0.67
];
figure(1)
plot(Data,'linewidth',1.0)
grid
legend('C1','C2','C3','C4','C5')
x=0:15;
x=x';
c1=Data(:,1);
c2=Data(:,2);
c3=Data(:,3);
c4=Data(:,4);
c5=Data(:,5);
f1 = fit(x(5:16),c1(5:16),'exp1');
f2 = fit(x(5:16),c2(5:16),'exp1');
f3 = fit(x(5:16),c3(5:16),'exp1');
f4 = fit(x(5:16),c4(5:16),'exp1');
f5 = fit(x(5:16),c5(5:16),'exp1');
figure(2)
plot(f1,'b')
hold on
plot(f2,'r')
plot(f3,'g')
plot(f4,'m')
plot(f5,'k')
yline(1.5228, '--')
grid
axis([0 17 0 7.5])
legend('C1','C2','C3','C4','C5')
Thank you.
  2 个评论
Torsten
Torsten 2022-2-20
f1(0),...,f5(0) are the y-intercepts.
Sarfaraz Ahmed
Sarfaraz Ahmed 2022-2-20
编辑：Sarfaraz Ahmed 2022-2-20
Thank you for your answer. Actually, this one for y-intercept. I want to get intercept with yline(1.5228, '--').
for example, in the attached figure intercept for "f1" is "12.492". however when I display f1 it shows y-intercept not y-line intercept. can you please let me know how can I get intercept with y-lines ? I corrected a question little bit as well.
Thank you

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采纳的回答

Torsten
Torsten 2022-2-20
编辑：Torsten 2022-2-20
a = f1.a;
b = f1.b;
xintercept1 = 1/b*log(1.5228/a);
(Same for f2,f3,f4 and f5)

更多回答（1 个）

DGM
DGM 2022-2-20
编辑：DGM 2022-2-20
Ran in:
Consider the example:
Data=[
0.11 0.3 0.28 0.6 0.31
0.23 0.78 0.57 1.08 0.43
0.26 0.95 0.84 1.25 0.46
0.55 1.2 1.1 1.5 0.75
6.95 7.05 8.25 7.35 7.15
5.2 4.34 4.68 4.64 5.4
4.81 4.74 4.21 5.04 5.01
3.96 4.07 3.96 4.37 4.16
3.88 3.78 3.25 4.08 4.08
2.69 2.4 2.81 2.7 2.89
2.36 2.35 2.7 2.65 2.56
2.24 2.28 2.35 2.58 2.44
1.9 2.07 1.94 2.37 2.1
1.7 1.95 1.68 2.25 1.9
0.57 1.67 1.47 1.97 0.77
0.47 0.89 1.1 1.19 0.67
];
ymark = 1.5228; % need to be able to use this
x = (0:15).';
plotcolors = {'b','r','g','m','k'};
f = cell(size(Data,2),1);
fk = zeros(size(Data,2),2);
for kn = 1:numel(f)
f{kn} = fit(x(5:16),Data(5:16,kn),'exp1');
fk(kn,:) = coeffvalues(f{kn});
plot(f{kn},plotcolors{kn})
hold on
end
yline(ymark, '--');
grid
axis([0 17 0 7.5])
intx = log(ymark./fk(:,1))./fk(:,2); % inverse of fit function
plot(intx,ymark,'kx') % show with marker
legend('C1','C2','C3','C4','C5')

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