FUN must be a function, a valid character vector expression, or an inline function object. | fzero

function T = FA(y)

for i = 1:length(y)
if y(i) >= 12.5
    N1(i)= 0
    N2(i)= 8 
    N3(i)= 9
    N4(i)=3.76*y(i)
    N5(i)= y(i)-12.5

else
    N1(i)= 2*(12.5 -y(i))
    N2(i)= 2*(y(i) - 8.5)
    N3(i)= 0
    N4(i)=3.76*y(i)
    N5(i)= 0
end

f{i}=@(T)-5078905.27 + N1(i)*(297334.224)+ N1(i)*((299180+37.85*(T)+(-4571.9)*log(T))-294170.430054)+N2(i)*((56835+66.27*(T)+(-11634)*log(T))-24557.403501)+N3(i)*((88923+49.36*(T)+(-7940.8)*log(T))-69574.657860)+N4(i)*((31317+37.46*(T)+(-4559.3)*log(T))-26135.539906)+N5(i)*((43388+42.27*(T)+(-6635.4)*log(T))-27886.197583)
fzero(f,2500)

end

I know that if I change f{i} to f(i) I'll be able to run the script and input whatever values I want. However, I need this script tor work in conjuction with this one

clc; clear; close all;

r = .7:.1:2.0;
y = 12.5*r

T = FA2(y);

I eventually want to plot the r values vs. the T values (fzero outputs). If I change f{i} to f(i) I get a different error code on the second script, "Nonscalar arrays of function handles are not allowed; use cell arrays instead."

What do I need to do to make these work together? Thank you

[Stephen23]

"I know that if I change f{i} to f(i) I'll be able to run the script and input whatever values I want."

No, actually you will get an error (because function handles cannot be put into an array).

Answer 1

[Stephen23]

You don't need to store the functions in any array, you only need to store the output values:

function out = FA(y)
out = nan(size(y));
for k = 1:numel(y)
    ...
    fun = @(T)...;
    out(k) = fzero(fun,2500);
end
end

[Vickson Leji]

When I try to run this script

clc; clear; close all;

r = .7:.1:2.0;
y = 12.5*r
out(k) = FA2(y);

plot(r,T)
title('Adiabatic Flame Temperature vs. Y/Ycc')
xlabel('Y/Ycc')
ylabel('Adiabatic Flame Temperature, Tp')

I'm getting this error

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

Error in fzero (line 322)
    elseif ~isfinite(fx) || ~isreal(fx)

Error in FA2 (line 24)
out(k) = fzero(f,2500);

Error in FA2run (line 5)
out(k) = FA2(y);

[Stephen23]

@Vickson Leji: as the fzero help clearly states, the function must accept and return a scalar value. So you need to fix your function so that it returns a scalar output value.