# How create a interaction method to re-calculate a equation if a condition is not satisfied

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Gabriel on 9 Dec 2013
Commented: sixwwwwww on 10 Dec 2013
I have a equation where i need to input a value and calculate some equations with this value.
In the end, i need to check if this value is ok.
If it's not, I need to input a new value and calculate the equation again with this new value.
Somebody can help me?
I tried this way.
I need to input "Tin" and calculate "Tw". In the end, i need check if the average between Tw and "Tb" in less than 10%. If it's not i neet to input a new value for "Tave".
clear
close all
Tin=input('Input T');
D=5;
t=0.362;
E=2.9e07;
ws=17.9148297590378;
R=1448.88;
alfa=1.96;
h=R*(1-(cos(alfa/2)));
I=pi*(D-t)*(D-t)*(D-t)*t/8;
teta=19.45;
L=495.73;
conv=teta*pi/180;
mis=0.3;
mil=0.05;
DRAG= 12*pi*D*L*mil;
Tb=8.89e4;
G=Tin;
for i=1:100
G(i)=Tin(i);
J=sqrt(E*I/G(i));
U=12*L/J;
X=3*L-(J/2)*tanh(U/2);
Y=18*L*L-J*J*(1-(1/cos(U/2)));
N=(12*G(i)*h-(ws/12)*cos(teta)*Y)/X;
frictc=N*mis;
ter=ws*L*sin(conv);
deltac=2*frictc+DRAG-ter;
Tw=deltac+Tb;
Tave(i)=(Tw+Tb)/2;
if Tave(i)>G(i)+G(i)*0.1
G(i)=Tave(i);
elseif Tave2(i)<G(i)-G(i)*0.1
G(i)=Tave2(i);
else
display(Tave2(i));
end
end
##### 2 CommentsShowHide 1 older comment
Gabriel on 9 Dec 2013
I'm sorry
New value for "Tin" if "Tave" is greater than 10% of "Tin".
Now the sentence is correct

sixwwwwww on 9 Dec 2013
Edited: sixwwwwww on 9 Dec 2013
try this:
Tin=input('Input T');
D=5;
t=0.362;
E=2.9e07;
ws=17.9148297590378;
R=1448.88;
alfa=1.96;
h=R*(1-(cos(alfa/2)));
I=pi*(D-t)*(D-t)*(D-t)*t/8;
teta=19.45;
L=495.73;
conv=teta*pi/180;
mis=0.3;
mil=0.05;
DRAG= 12*pi*D*L*mil;
Tb=8.89e4;
G(1) = Tin;
for i=1:100
J=sqrt(E*I/G(i));
U=12*L/J;
X=3*L-(J/2)*tanh(U/2);
Y=18*L*L-J*J*(1-(1/cos(U/2)));
N=(12*G(i)*h-(ws/12)*cos(teta)*Y)/X;
frictc=N*mis;
ter=ws*L*sin(conv);
deltac=2*frictc+DRAG-ter;
Tw=deltac+Tb;
Tave(i)=(Tw+Tb)/2;
if Tave(i) >= Tin * 0.1
Tave(i) = input('Enter new value of Tave:');
end
G(i + 1) = Tave(i);
end
display(Tave(i))
sixwwwwww on 10 Dec 2013
Yes value of Tw is changing in each for loop iteration and so Tave also changes each time

### More Answers (2)

Walter Roberson on 9 Dec 2013
need_to_continue = true;
while need_to_continue
Tin = input('Temperature In');
....
need_to_continue = (Tw + Tb)/2 > Tb/10; %average is more than 10% ?
end

Gabriel on 10 Dec 2013
Thanks so much..
It's running perfectly now...
##### 1 CommentShowHide None
sixwwwwww on 10 Dec 2013
you are welcome