How to add three if else conditions?

Question

Shantanu K 2013-3-12

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/66844-how-to-add-three-if-else-conditions

Here one if else loop is used. there i have used three conditions i want to use and operator.....means if all conditions are satisfied then it should display given function !

Sigma_x=-500;
Sigma_y=-500;
Sigma_xy=00;
theta=0;
o=(pi)*theta/180;
T=[cos(o) -sin(o); -sin(o) cos(0)];
Q= T*[Sigma_x Sigma_xy; Sigma_xy Sigma_y]/(T');
Sigma1=Q(1,1);
Sigma12=Q(1,2);
Sigma2=Q(2,2);
S1t=1300;
S1c=-700;
S2t=1200;
S2c=-500;
S6=600;
S1=(S1c:S1t);
S2=(S2c:S2t);
plot(S1t,S2);
hold on;
plot(S1c,S2);
hold on;
plot(S1,S2t);
hold on;
plot(S1,S2c);
plot(Sigma1,Sigma2,'*')
axis([-800 1600 -800 1600])
xlabel('Sigma1')
ylabel('Sigma2')
title('Maximum Stress Theory')
if (S1c<Sigma1<S1t); 
    and   
    (S2c<Sigma2<S2t);
    and    
    (0<Sigma12<S6);
    display('Its safe zone');
else
    display('Material has yielded');
end
%end

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Answer 1

Friedrich 2013-3-12

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/66844-how-to-add-three-if-else-conditions#answer_78299

编辑：Friedrich 2013-3-12

在 MATLAB Online 中打开

Hi,

do it like this

if ((S1c<Sigma1) && (Sigma1<S1t) && (S2c<Sigma2) && (Sigma2<S2t) && (0<Sigma12) && (Sigma12<S6))
    display('Its safe zone');
else
    display('Material has yielded');
end

You have to split up things like a<b<c into a<b && b<c otherwise you can get unwanted behavior, e.g.

>> 1<2<3 %yay it works
ans =
       1
>> 1<pi<3 %oh wait it doesnt!
ans =
       1

This happens because of the way MATLAB parses such an expression. It parses from left to right, so 1<pi is true, so 1. Then 1 < 3 is also true so you get true at the end. But thats not want you want