plotting function which contain zero denominator term

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shree thapa
shree thapa 2021-1-29
评论： Walter Roberson 2021-1-29
I have a function : . I need to plot a graph between x Vs g(x) where
, I just need values of x from o to ∞ without x=1 because it will give me which doest not make sense.
My Question: How can I use "if and elseif" syntax to plot grap between x Vs g(x) excluding value x=1 and inclusing rest of others.
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Walter Roberson
Walter Roberson 2021-1-29
Okay, so suppose I choose x = 7. Then what would the expected plot be? is constant because the integral "uses up" all of the unbound variables in f(x)
shree thapa
shree thapa 2021-1-29
Yes, You right x is variable so you will get different g(x) for different x so the just plot.

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回答（1 个）

Walter Roberson
Walter Roberson 2021-1-29
Ran in:
syms x
f(x) = 1/(1-x^2)
f(x) = 
g(x) = int(f(x), x, 0, inf)
g(x) = 
NaN
g(x) is always undefined, no matter what the value of x is.
ratio = f(x)/g(x)
ratio = 
NaN
fplot(ratio, [0 20])
Notice the plot is empty. Because every entry is NaN.
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Walter Roberson
Walter Roberson 2021-1-29
Ran in:
syms x
f(x) = piecewise(x < 1, 1/(1-x^2), x == 1, 0, -1/(1-x^2))
f(x) = 
a = int(f(x), x, 0, 1)
a = 
∞
b = int(f(x), x, 1, inf)
b = 
∞
a+b
ans = 
∞
g(x) = int(f(x), x, 0, inf)
g(x) = 
∞
ratio = f(x)/g(x)
ratio = 
0
fplot(ratio, [0 20])
So you can define away the integral so that you do not get nan (by integrating a different function), but you are stuck with the problem that g(x) is constant.

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