why this program showing error like undefined variable.?..one day before same program was giving results but now it os showing error.please help

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an 2014-3-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/123301-why-this-program-showing-error-like-undefined-variable-one-day-before-same-program-was-giving-res

回答： Joseph Cheng 2014-3-27

Pc=620*10^6                            
Pa=62*10^9                         
Ps=1*10^9                          
r=10                                
d=1:10:1000                       
s=(d./r)
s1=s
w1=4.3                           
E0=8.85*10^-12                    
Eb=6.830890.*(w1.^(3/2))         
A1=d.^2                          
B1=(d./d0).^(1/3)                 
l=(Eb./B1)                          
m= (2.*Pc./E0).^(1/2)
n=(8.*Pa./(E0.*(1+s).^4)).^(1/2)
x1=min(m,n)
Es=min(x1,l)
h=8
l1= 0.5.*E0.*l.^2.*10^18
n1=(4.*Pa)./((1+(s)).^4)
y1=min(l1,Pa)
y2=min(y1,n1)
if  s1<=2
    e1=1
elseif s1>=2
        e1= (s+2)./4
elseif  s1>2;
            e1=(d./r)./4
end
x1=e1;
A1=d.^2
u=e1.*y2                
A2=(A1.*Ps)./u          
A=(A1+A2)                   
x2=(d+h)
Vw=(d.*A1)./(x2.*A)        
uw=(u.*Vw)                 
plot(d,uw)

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Mischa Kim 2014-3-27

在 MATLAB Online 中打开

As pointed out above by RAGHAVENDRA, there is no assignment for e1 in the final else

 else
    e1 = 0;  % add some statement to assign a value
 end

I strongly suspect that your code jumps right into the else, no value for e1 is assigned, which results in the error message.

an 2014-3-27

yes, the code directly jumps to else statement it is not computing the if else values.

how to assign value for e1, e1 is a variable only.

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采纳的回答

Joseph Cheng 2014-3-27

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/123301-why-this-program-showing-error-like-undefined-variable-one-day-before-same-program-was-giving-res#answer_130723

My answer to why it worked one day and not another would be pasted code is a script. The issue with scripts is that if you do not clear the workspace before running it multiple times value may not be cleared. So if it is defined during debugging or in a previous iteration it will still be defined until you close down matlab or clear the workspace.