How to add a vertical line in a plot that corresponds to a maximum?
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Petros Tsitouras
el 5 de Jul. de 2019
Comentada: Star Strider
el 5 de Jul. de 2019
Hello, everyone!
I would like to add a vertical line corresponding to the maximum value of the graph attached (and displaying its value). Basically, I need a line that is 'x= fundamental frequency' . I know that similar questions are already answered in the forum, but could not find something working for me. Below I have attached the code and the audio file, accompanied with the last graph that I want to add the line to. Thank you very much in advance!
close all;
clear all;
clc;
%______________________________________________________
[y, Fs] = audioread('A1-sound.wav');
t=linspace(0,length(y)/Fs, length(y));
Fn = Fs/2;
L = length(y);
Y = fft(y);
phase2 = abs(Y/L);
phase1 = phase2(1:L/2+1);
phase1(2:end-1) = 2*phase1(2:end-1);
F = Fs*(0:(L/2))/L;
%_______________________________Frequencies Distribution
figure;
subplot(2,1,1);
plot(F,phase1);
title('Amplitude Spectrum of Signal');
xlabel('Frequency (Hz)');
ylabel('Absolute Amplitude of Frequencies (dB)');
%__________________________________________________Focus
idx = F >= 0 & F <= 1000; %Focusing 0-1000 Hz
zoomX = F(idx);
zoomY = phase1(idx);
subplot(2,1,2);
plot(zoomX, zoomY);
title('Amplitude Spectrum of Signal');
xlabel('Frequency (Hz)');
ylabel('Absolute Amplitude of Frequencies (dB)');
%________________________________________Fundamental Frequency
[maxValue, f1] = max(Y);
idx2 = F >= 80 & F <= 120; %Focusing 80-120 Hz
zoomX2 = F(idx2);
zoomY2 = phase1(idx2);
figure;
plot(zoomX2, zoomY2);
title('Amplitude Spectrum of Signal');
xlabel('Frequency (Hz)');
ylabel('Absolute Amplitude of Frequencies (dB)');
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Star Strider
el 5 de Jul. de 2019
Changing part of your code to draw the vertical lines, and the text label in figure(2):
%__________________________________________________Focus
idx = F >= 0 & F <= 1000; %Focusing 0-1000 Hz
zoomX = F(idx);
zoomY = phase1(idx);
subplot(2,1,2);
plot(zoomX, zoomY);
title('Amplitude Spectrum of Signal');
xlabel('Frequency (Hz)');
ylabel('Absolute Amplitude of Frequencies (dB)');
[pks1,locs1] = findpeaks(zoomY, 'MinPeakProminence',0.002, 'MinPeakDistance',100); % Identify Prominent Peaks ...
hold on
ylv = ylim;
plot([1;1]*zoomX(locs1), ylv(:)*ones(size(pks1'))) % ... & Plot Vertical Lines Through Them
hold off
%________________________________________Fundamental Frequency
[maxValue, f1] = max(Y);
idx2 = F >= 80 & F <= 120; %Focusing 80-120 Hz
zoomX2 = F(idx2);
zoomY2 = phase1(idx2);
figure;
plot(zoomX2, zoomY2);
title('Amplitude Spectrum of Signal');
xlabel('Frequency (Hz)');
ylabel('Absolute Amplitude of Frequencies (dB)');
[pks2,locs2] = max(zoomY2); % Identify Prominent Peak ...
hold on
plot([1;1]*zoomX2(locs2)', ylv(:)*ones(size(pks2'))) % ... & Plot Vertical Line Through It
text(zoomX2(locs2), pks2/2, sprintf('\\leftarrow %.1f Hz = Fundamental Frequency',zoomX2(locs2)), 'HorizontalAlignment','left')
I wasn’t certain if you also wanted the vertical lines in the lower subplot, so I used findpeaks to add them as well. The peak in figure(2) kist needs max, since ther is only one peak.
Experiment to get the result you want.
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