Problem with While loop

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fabian
fabian 2015-9-20
评论： fabian 2015-9-20
Hello friends, I want to ask for help in the following code, and I use the while loop to determine the vectors must be below a value but I generated will last value that is not less, that I make only store the while smaller and open. Thank you.
clear
clc
H=[0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3500 3750 4000 5000];
B=[0 0.4 0.8 1 1.15 1.25 1.32 1.38 1.41 1.44 1.46 1.48 1.5 1.53 1.54 1.55 1.6];
%******************************************
A=27e-4;
l=[0.8 0.8 0.6];
N=2000;
b=length(B);
fmax=B(b)*A;
flujo1=0:fmax/30:fmax;
B1=flujo1/A;
H1=interp1(B,H,B1,'pchip');
H2=(H1*l(1))/l(2);
B2=interp1(H,B,H2,'pchip');
f2=B2*A;
f3=flujo1+f2;
B3=f3/A;
H3=interp1(B,H,B3,'pchip');
I=(H3*l(3)+H2*l(2))/N;
i=1;e=0;
while e<max(B)
Fr1(i)=flujo1(i);
Fr2(i)=f2(i);
Fr3(i)=f3(i);
Ir(i)=I(i);
e=B3(i);
i=i+1;
end
hold on
plot(Ir,Fr1,'+')
plot(Ir,Fr2,'r')
plot(Ir,Fr3,'-o')
grid on
legend ('Flujol','Flujo2','Flujo3')
title('CURVA DE EXCITACIÓN CORRIENTE vs FLUJO')
xlabel('Corriente(A)')
ylabel('Flujo(Wb)')
pause
hold off

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回答（1 个）

Walter Roberson
Walter Roberson 2015-9-20
last_e = e;
while e<max(B)
Fr1(i)=flujo1(i);
Fr2(i)=f2(i);
Fr3(i)=f3(i);
Ir(i)=I(i);
last_e = e;
e=B3(i);
i=i+1;
end
e = last_e;
Now after the loop, e will be the last value for which the condition was true, rather than being the first value for which the condition was false.
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Walter Roberson
Walter Roberson 2015-9-20
The condition is not changed until you do
e=B3(i);
so the code is storing only the values before the condition.
Perhaps you wanted to change your condition.
Fr1 = [];
Fr2 = [];
Fr3 = [];
Ir = [];
i=1;
while B3(i) < max(B)
Fr1(i) = flujo1(i);
Fr2(i) = f2(i);
Fr3(i) = f3(i);
Ir(i) = I(i);
i=i+1;
end
You could make this much more compact:
idx = find(B3 >= max(B), 1, 'first');
i = idx - 1;
Fr1 = flujo1(1:i);
Fr2 = f2(1:i);
Fr3 = f3(1:i);
Ir = I(1:i);

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