analytical solution of ODEs

%calculating the analytical solution for d^2T/dr^2 + 1/r dT/dr = 0

syms r

r = linspace(0.005,0.1,10);

dT = dsolve('1*D2r+((1/r(i))*Dr) =1','r(0.005)=200','r(0.1)=80')

plot(r,dT)

keep getting this error

Error using plot

Data must be numeric, datetime, duration or an array convertible to double.

Error in FD_6a (line 31)

plot(r,dT)

Answer 1

[Bjorn Gustavsson]

This should be done thisly:

syms r
syms T(r)
dTdr = diff(T)
d2Tdr2 = diff(T,2)
T = dsolve(1*d2T+((1/r)*dT) ==1,T(0.005)==200,T(0.1)==80)
Tfun = matlabFunction(T)
r_doble = linspace(0.005,0.1,321);
plot(r_double,Tfun(r_double))

HTH

[Ronald Aono]

still getting the folowing error

Undefined function or variable 'd2T'.

Error in FD_6a (line 30)

T = dsolve(1*d2T+((1/r)*dT) ==1,T(0.005)==200,T(0.1)==80 )