how to get maximum value of this code

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kyungdoo lee
kyungdoo lee 2021-10-26
评论： Star Strider 2021-10-26
T = readtable('data1.xlsx') ;
T = table2array(T) ;
x = T(1,2:end); % coil length
y = T(2:end,1); % magnitude length
Z = T(2:end,2:end); % use fillmissing to fill NaNs
[X,Y] = meshgrid(x,y) ;
[xq,yq] = meshgrid(2:0.1:10); % grid interval 0.1
Zq = interp2(x,y,Z,xq,yq,'spline');
figure
AA = surf(xq,yq,Zq);
title('(spline,cubic,makima) Interpolation Using Finer Grid');
%%
% example
% if input (1, 1), in interpolation (2.0, 2.0)
% if input (23, 23) , in interpolation (42, 42)
% if input (81, 81) , in interpolation (10.0 , 10.0)
% Upper limit& Lower limit are 1~81
Zq(1,1)
Zq(23,23)
Zq(81,81)
%% optimmization algorithm
% source : https://sites.google.com/a/hydroteq.com/www/
clc
% HS: Harmony Search minimization
% Use the Matlab startup random number sequence:
rand('twister',5489); % Commment out to start rand from current position
% Specify objective function and bounds
f = Zq;
xL = [0.01 0.01]; % minimum range
xU = [0.81 0.81]; % maximum range
% Set HS algorithm parameters
HSparams.HMS = 10;
HSparams.MaxImp = 10000;
HSparams.HMCR = 0.8;
HSparams.PAR = 0.4;
HSparams.b = (xU-xL)/1000;
% Perform minimization
[xbest,fbest] = harmony(f,xL,xU,HSparams);
fprintf('Best solution found:\n')
disp(xbest)
fprintf('Function value = %f\n', fbest)
I want to find maxinmum of attached table. But when I use this code I get the minimum.
What should I fix to get the maximum value?

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采纳的回答

Star Strider
Star Strider 2021-10-26
Ran in:
Important parts of the code appear to be missing.
However to get the maximum, negate the function —
f = @(x) sin(x);
x0 = rand;
[minimum,fvmin] = fminsearch(f, x0)
minimum = -1.5708
fvmin = -1.0000
[maximum,fvmax] = fminsearch(@(x)-f(x), x0)
maximum = 1.5708
fvmax = -1.0000
figure
plot((-pi:0.1:pi), sin((-pi:0.1:pi)))
hold on
plot(minimum,f(minimum),'vr', maximum,f(maximum),'^r')
hold off
legend('Function','Minimum','Maximum', 'Location','best')
ylim(ylim*1.1)
.
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