Help with MATLAB code; discrepancy between graph's max and Matlab's max
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Hi,
For some reason, when I run this MATLAB code, I'm getting what looks like about 10,000 for Rf for the largest Vo on the graph, but matlab is giving me Rf at (Vo)max as 100,001
Any ideas?
clc; clear; close all;
syms Rf
Rf = 0:0.1:100000;
VRt25 = 18.*(10000)./(10000 + Rf); VRf25 = 18.*(Rf)./(10000 + Rf);
VRt2505 = 18.*(9977.81)./(9977.81 + Rf); VRf2505 = 18.*(Rf)./(9977.81 + Rf);
V_difference25 = abs(VRt25 - VRf25);
V_difference2505 = abs(VRt2505 - VRf2505);
Vo_difference = abs(V_difference25 - V_difference2505);
figure;
plot(Rf,Vo_difference)
title('Voltage Difference Vo vs. Rf')
ylabel('Vo Difference [V]')
xlabel('Rf [ohms]')
hold on
%Maximum Vo Difference
[Vo_difference_max,Rf] = max(Vo_difference)
Thank you all!
采纳的回答
Image Analyst
2014-2-16
The max() function returns the index of Vo_difference, not Rf directly. Plus Rf starts at 0 not 1. Try this:
Rf = 0 : 0.1 : 100000;
VRt25 = 18.*(10000)./(10000 + Rf); VRf25 = 18.*(Rf)./(10000 + Rf);
VRt2505 = 18.*(9977.81)./(9977.81 + Rf); VRf2505 = 18.*(Rf)./(9977.81 + Rf);
V_difference25 = abs(VRt25 - VRf25);
V_difference2505 = abs(VRt2505 - VRf2505);
Vo_difference = abs(V_difference25 - V_difference2505);
figure;
plot(Rf,Vo_difference)
title('Voltage Difference Vo vs. Rf')
ylabel('Vo Difference [V]')
xlabel('Rf [ohms]')
hold on
%Maximum Vo Difference
[Vo_difference_max, indexAtMax] = max(Vo_difference)
RfAtMax = Rf(indexAtMax)
message = sprintf('The Rf at max Vo = %f.', RfAtMax);
helpdlg(message);
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