how to implement Bessel's function in MATLAB

2021 1 16
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更新时间：2021 2 10
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i want to find the solution of this bessels function mentioned
please help me to model the same in matlab or simulink

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Walter Roberson
Walter Roberson 2021-1-16
编辑：Walter Roberson 2021-1-16

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https://www.mathworks.com/help/matlab/ref/besselj.html for the numeric version
https://www.mathworks.com/help/symbolic/besselj.html for the symbolic version
When Bessel functions are being used, it is not uncommon to find that you need higher precision than double precision can provide, so it is common to need to use the symbolic version. To be more precise, often calculation of the values needs a higher range than double precision can support: it is common to end up with formulas that involve the ratio of two large numbers, and even though the ratio might be in the 1/1000 to 2 range, the individual numbers overflow to infinity in double precision.

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NIHAD MOHAMED ALI
NIHAD MOHAMED ALI 2021-1-16
could you be more specific, on how to implement that equation in matlab
NIHAD MOHAMED ALI
NIHAD MOHAMED ALI 2021-2-10
how do i implement J1'(sigma) ?
Walter Roberson
Walter Roberson 2021-2-10
Ran in:
Ran in:
syms sigma
J1prime(sigma) = diff(besselj(1,sigma))
J1prime(sigma) = 
vpa(J1prime(3))
ans = 
NIHAD MOHAMED ALI
NIHAD MOHAMED ALI 2021-2-10
编辑：NIHAD MOHAMED ALI 2021-2-10
sigma=1.469;
x=besselj(1,sigma);
y=bessely(1,sigma);
z=diff(besselj(1,sigma));
vpa(z);
what am i doing wrong?
am geting answer as zero
NIHAD MOHAMED ALI
NIHAD MOHAMED ALI 2021-2-10
@Walter Roberson specific thing is i need to solve equation 2 and use the result in equation 3! so am studying the basics you been of great help,but iam still having trouble cracking it
Walter Roberson
Walter Roberson 2021-2-10
编辑：Walter Roberson 2021-2-10
Ran in:
Ran in:
format long g
sigma=1.469
sigma =
1.469
x = besselj(1,sigma)
x =
0.553407191636554
y = bessely(1,sigma)
y =
-0.432787705894754
syms Sigma
J1prime(Sigma) = diff(besselj(1,Sigma))
J1prime(Sigma) = 
z = J1prime(sigma)
z = 
vpa(z)
ans = 
0.15233074502500402865842627859807
Walter Roberson
Walter Roberson 2021-2-10
Ran in:
Ran in:
Remember, besselj(1,sigma) is a constant value, and diff() of a constant value is 0. You did something similar to
syms X
f(X) = X^2
f(X) = 
x = 3
x = 3
diff(f(x))
ans = 
0
df = diff(f)
df(X) = 
df(x)
ans = 
6
When x is a particular number, f(x) is a point, not a line, and diff() of a point is 0. You need to differentiate the function and then substitute the particular number into the result.
NIHAD MOHAMED ALI
NIHAD MOHAMED ALI 2021-2-10
yes, clealy understood my mistake ; thanks a bunch

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