Invalid use of operator

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Maria Mamai
Maria Mamai 2021-9-24
评论： Maria Mamai 2021-9-24
I try to make the graph of this equation:
I(a) = a^6 * (K1 *K3 - K2^2)
where
a = [0,5,100]
K1 = besselk(1,a)
K3 = besselk(3,a)
K2 = besselk(2,a)
my code is
I = (a.^6)*(K1.*K3.-K22.)
and I get "invalide use of operator" for (-) symbol. I can not understand why. Can please anyone help?

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回答（1 个）

Fangjun Jiang
Fangjun Jiang 2021-9-24
There is a difference between operator "*" and ".*". But there is no such an operator as ".-" in MATLAB.
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Walter Roberson
Walter Roberson 2021-9-24
Ran in:
a = [0,5,100]
a = 1×3
0 5 100
K1 = besselk(1,a)
K1 = 1×3
Inf 0.0040 0.0000
K3 = besselk(3,a)
K3 = 1×3
Inf 0.0083 0.0000
K2 = besselk(2,a)
K2 = 1×3
Inf 0.0053 0.0000
I = (a.^6) .* (K1 .* K3 - K2.^2)
I = 1×3
NaN 0.0836 0.0000
Maria Mamai
Maria Mamai 2021-9-24
Thank you very much!

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