Why do I get Inf for this complex expression?

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Daniel Montgomery 2020-6-2

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回答： Ayden Clay 2020-6-2

I have a function that generates a complex number but I get Inf for x. how could this be, if I do not make a logical error

for f=1:100

%a and b are struct passed by value, e.g. sturct(1).field

[R1,R2] = Prop(a(f),b(f),f,constant(f))

{e1=cell2mat(a)+cell2mat(b);

e2=cell2mat(a)-cell2mat(b);

w=(1-e1.*e2)./(e1-e2);}

end

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Daniel Montgomery 2020-6-2

e.g. sturct(1).field=1+j

e.g. sturct(1).field2=2+j3.5

David Goodmanson 2020-6-2

Hi Daniel,

if you mean that you get inf for w, then on the basis of the information given the most obvious possibliity is that for at least one value of f the value of cell2mat(b) is zero.

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Answer 1

Ayden Clay 2020-6-2

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Hi Daniel,

So in MATLAB there are only a few ways to get an output of "inf". The most common in equations is that we are dividing by zero.

In this case since w = (1-e1*e2)/(e1-e2), it must be the case that for some f, e1 = e2. This can only be the case if a+b = a-b which is only possible if b = -b, which is only possible if b = 0.