Hi All
just having the vectors of the axes , how can I find the minimums ?
MATLAB: How to find both of the local minimums in this plot
minimumplotSignal Processing Toolbox
Related Solutions
You may be making this too difficult.
Example —
a = linspace(0, 4*pi);y = sin(a);[pks,pkloc] = findpeaks( y,a); % Maxima
[vls,vlloc] = findpeaks(-y,a); % Minima
figure(1)plot(a, y, '-b')hold onplot(pkloc, pks, '^r', 'MarkerFaceColor','r')plot(vlloc, -vls, 'vg', 'MarkerFaceColor','g')hold offgridaxis([xlim -1.1 1.1])legend('Data', 'Peaks', 'Valleys')Note that to plot the valleys (‘vls’) or minima correctly, simply negate them in the plot call. So to find them, use:
[vls,vlloc] = findpeaks(-y,a); % Minimaand to plot them or use them in other calculations correctly, negate them again to restore their correct values:
plot(vlloc, -vls, 'vg', 'MarkerFaceColor','g')This will do it:
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;format compact;fontSize = 20;s = load('data.mat')data = s.data;hFig = figure;plot(data, 'b-', 'LineWidth', 2)grid on;xlabel('Index', 'FontSize', fontSize);ylabel('Signal', 'FontSize', fontSize);% Maximizxe the window.
hFig.WindowState = 'maximized';% Find the max
[maxValue, indexOfMax] = max(data)% Find the min
[minValue, indexOfMin] = min(data)% Find out where the signal last crosses 0 before the peak
% First set after the peak to infinity so we do not find that.
tempSignal = data;tempSignal(indexOfMax:end) = inf;indexLeft = find(tempSignal < 0, 1, 'last')% Plot a red spot there.
hold on;plot(indexLeft, data(indexLeft), 'r.', 'MarkerSize', 40);% Find out where the signal first crosses 0 after the max peak on the right side.
% First set before the valley to infinity so we do not find the peak.
tempSignal = data;tempSignal(1 : indexOfMax) = inf;indexMiddle = find(tempSignal < 0, 1, 'first')% Plot a red spot there.hold on;plot(indexMiddle, data(indexMiddle), 'r.', 'MarkerSize', 40);% Find out where the signal first crosses 0 after the min peak (the biggest valley).
% First set before the valley to -infinity so we do not find the peak.
tempSignal = data;tempSignal(1 : indexOfMin) = -inf;indexRight = find(tempSignal > 0, 1, 'first')% Plot a red spot there.hold on;plot(indexRight, data(indexRight), 'r.', 'MarkerSize', 40);
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