Writing this Mathcad equation in Matlab

hi, Im trying to convert an equation from mathcad into matlab but am struggling. the equation is:

Answer 1

[Star Strider]

Try this:

psi = 0.142;
Io = 1;
f_vir2 = @(r) 4*Io * abs(integral(@(rho)besselj(0, pi*rho*r*psi).*rho, 0, 1)).^2;

r = pi;
test_call = f_vir2(r)

[Jason]

Thankyou Jason

[Star Strider]

As always, my pleasure.

If you are new to MATLAB, see the documentation on Anonymous Functions (link) to understand those I used here.

[Jason]

Hello, Im trying to plot the functional form as follows:

psi = 0.142;
Io = 1;
f_vir = @(r) 4*Io * abs(integral(@(rho)besselj(0, pi*rho*r*psi).*rho, 0, 1)).^2;
r = linspace(-20,20);
axes(handles.axes1); cla reset
plot(f_vir(r))

But get the following error:

Error using  * 
Inner matrix dimensions must agree.

Error in PSF>@(rho)besselj(0,pi*rho*r*psi).*rho (line 167)
f_vir = @(r) 4*Io * abs(integral(@(rho)besselj(0, pi*rho*r*psi).*rho, 0, 1)).^2;

Error in integralCalc/iterateScalarValued (line 314)
                fx = FUN(t);

Error in integralCalc/vadapt (line 132)
            [q,errbnd] = iterateScalarValued(u,tinterval,pathlen);

[Torsten]

f_vir = @(r) 4*Io * abs(integral(@(rho)besselj(0, pi*rho*r*psi).*rho, 0, 1,'ArrayValued',true)).^2;

plot(r,f_vir(r))

[Jason]

Thankyou. whats the reason for "ArrayValued", "true" Jason

[Torsten]

You call "f_vir" with an array of values for r, "integral" usually calls "f_vir" with an array of values for rho. This would usually make multiplications of the form "r*rho" within "f_vir" incompatible. To avoid this conflict in lengths, the "ArrayValued=true" option tells "integral" to call "f_vir" only with a single scalar for "rho".

You could also use

r=linspace(-20,20);
for i=1:numel(r)
  f_vir_array(i)=f_vir(r(i));
end
plot(r,f_vir_array)

without the "ArrayValued=true" option.

Best wishes

Torsten.

[Jason]

Thankyou again

[Star Strider]

@Torsten — Thank you.

@Jason — Our pleasure.