Invalid use of operator

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?

Answer 1

[Fangjun Jiang]

There is a difference between operator "*" and ".*". But there is no such an operator as ".-" in MATLAB.

[Maria Mamai]

Do you know how can I fix that?

[Walter Roberson]

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]

Thank you very much!