How to find the max value of a curve on a graph

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Will Jeter
Will Jeter 2020-11-12
回答： KSSV 2020-11-12
I'm trying to find the max value of my G(T) curve(the parabolic one). Not sure how to het the value and make it show up as a marker on the graph
T = [310:1:450];
v = 1;
V = 10;
dHrxn = -80000;
UA = 3600;
kf0 = 1;
kc0 = 100;
T0 = 400;
ER = 20000;
CpA = 40;
kf = exp(-20000*(1./T-1/400));
kc = 100*exp((80000/1.987)*(1./T-1/400));
x = 1./(v./(V.*kf)+1+(1./kc));
R = 400*(T-310);
R1 = 400*(T-256);
R2 = 400*(T-233.5);
R3 = 400*(T-218.2);
R4 = 400*(T-391);
R5 = 400*(T-328);
R6 = 400*(T-346);
R7 = 400*(T-353.2);
G = x*-dHrxn;
figure
hold all
plot(T,R,T,G,T,R1,T,R2,T,R3,T,R4,T,R5,T,R6,T,R7)
legend('R(T)','G(T)','Ta=250K','Ta=225K','Ta=208K','Ta=400K','Ta=330K','Ta=350K','Ta=358K','Location','NorthWest')
axis([310 450 0 10*10^4])
xlabel('Temperature (K)')
ylabel('G(T) and R(T) (cal/mol)')
title('G(T) and R(T) vs. T')

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回答（1 个）

KSSV
KSSV 2020-11-12
If (x,y) are the data points.
[val,idx] = max(y) ;
plot(x,y)
hold on
plot(x(idx),y(idx),'*r')

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