fzero returns "Too many input arguments"

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Danny Darby
Danny Darby on 29 Nov 2021
Commented: Star Strider on 30 Nov 2021
Function code:
function retf = f(pH, L, bl1, bl2, bl3, bh2, bh1, Ltot, MLratio)
Mtot = MLratio * Ltot;
H = 10^(-pH);
M = Mtot / (1 + bl1*L + bl2*bl1*L^2 + bl3*bl2*bl1*L^3);
Ltot_calculated = L + bl1*M*L + 2*bl2*bl1*M*L^2 + 3*bl3*bl2*bl1*M*L^3 + bh2*H^2*L + bh1*H*L;
retf = Ltot - Ltot_calculated;
end
Want to optimize retf to 0 at specified pH values by varying L
clear all vars
clc
bl1 = 10^(6.78);
bl2 = 10^(11.78);
bl3 = 10^(14.9);
bh2 = 10^(15.9);
bh1 = 10^(9.83);
Ltot = 0.04;
MLratio = 1/3;
'speciation_ni_his_varied_pH_function.m';
fun = @(L)f(7, L, bl1, bl2, bl3, bh2, bh1, Ltot, MLratio);
[L, fval, info, output] = fzero(fun, [0, Ltot]);
L / Ltot
L is an element of 0:Ltot

Accepted Answer

Star Strider
Star Strider on 29 Nov 2021
Perhaps the order in the code is wrong. The functions must all be at the end of the script for included functions to work.
This runs without error when I run i t here —
bl1 = 10^(6.78);
bl2 = 10^(11.78);
bl3 = 10^(14.9);
bh2 = 10^(15.9);
bh1 = 10^(9.83);
Ltot = 0.04;
MLratio = 1/3;
'speciation_ni_his_varied_pH_function.m';
fun = @(L)f(7, L, bl1, bl2, bl3, bh2, bh1, Ltot, MLratio);
[L, fval, info, output] = fzero(fun, [0, Ltot]);
L / Ltot
ans = 9.5868e-09
function retf = f(pH, L, bl1, bl2, bl3, bh2, bh1, Ltot, MLratio)
Mtot = MLratio * Ltot;
H = 10^(-pH);
M = Mtot / (1 + bl1*L + bl2*bl1*L^2 + bl3*bl2*bl1*L^3);
Ltot_calculated = L + bl1*M*L + 2*bl2*bl1*M*L^2 + 3*bl3*bl2*bl1*M*L^3 + bh2*H^2*L + bh1*H*L;
retf = Ltot - Ltot_calculated;
end
Experiment to get different results.
.

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R2020b

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