Can we find derivative of bessel functions in matlab directly?

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Javeria
Javeria 2025-7-3
移动：Torsten 2025-7-3
For example if i have x can be any value. I need to know how we can find the derivative directly in MATLAb. for m=0,1.

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Torsten
Torsten 2025-7-3
移动：Torsten 2025-7-3
Ran in:
You can compute it symbolically first and insert the result as a numerical expression in your code.
syms x
diff(besselj(0,x),x)
ans = 
diff(besselj(1,x),x)
ans = 

更多回答（1 个）

David Goodmanson
David Goodmanson 2025-7-3
编辑：David Goodmanson 2025-7-3
Hi Javeria,
Here is a function that produces J'm(x) for integer m.
function y = besseljd(n,x,opt)
% derivative of bessel function of integer order.
% input s is optional.
% if s = 1, result is scaled by exp(-abs(imag(z))), same as with besselj.
% default is 0, no scaling.
% note that there is another available expression besides the one used below:
% y = besselj(n-1,x,s) - n*besselj(n,x,s)./x;
%
% y = besseljd(n,x,s);
if nargin == 3
s = opt;
else
s = 0;
end
y = -besselj(n+1,x,s) + n*besselj(n,x,s)./x;
% get rid of nans, integer order
if n==1
y(x==0) = 1/2;
else
y(x==0) = 0;
end
  2 个评论
Javeria
Javeria 2025-7-3
Can we make use of only one line which calculate the derivative of bessel functions just we only switch cases i.e mode m= 0, 1.
David Goodmanson
David Goodmanson 2025-7-3
I'm not sure exactly what you mean but if scaling is not needed then the single line
y = -besselj(n+1,x) + n*besselj(n,x)./x;
works unless x = 0. If x = 0 then you still need the four last lines in the code above.

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