solving non linear equation

how can i return a vector as a solution?

I want back a number of roots equal to the number of values ​​of t

syms S

>> myfun = @(S,t) 0.17*((S/10.8)+(S/21.6*sqrt(1+16*((S/5.4)^2))+((1/16)*log((4*S/5.4)+sqrt(1+(16*(S/5.4)^2))))))- t

>> t = linspace(0,2.6,10)

>> fun = @(S) myfun(S,t)

S = fzero(fun,0.03)

The program return this error:

Operands to the || and && operators must be convertible to logical scalar values.

Error in fzero (line 327)

elseif ~isfinite(fx) || ~isreal(fx)

Answer 1

[Star Strider]

First:

vv = vectorize('0.17*((S/10.8)+(S/21.6*sqrt(1+16*((S/5.4)^2))+((1/16)*log((4*S/5.4)+sqrt(1+(16*(S/5.4)^2))))))- t')

then copy the result (between the single quotes) to the body of ‘myfun’.

After that (I have already done and copied the vectorized result):

myfun = @(S,t) 0.17.*((S./10.8)+(S./21.6.*sqrt(1+16.*((S./5.4).^2))+((1./16).*log((4.*S./5.4)+sqrt(1+(16.*(S./5.4).^2))))))- t;
t = linspace(0,2.6,10)
for k = 1:numel(t)
    S(k) = fzero(@(S) myfun(S,t(k)),0.03);
end

and you get the result you want.

[RAFFAELE CANTERI]

thanks!

[Star Strider]

As always, my pleasure!