how to draw a peak line

Hi, i've data and i want to draw a line that corresponds to the peaks (where there is a zero the previous value >0 must be pasted) (See black line painted)

Is there a function or graph type that does this to me?

Answer 1

[Star Strider]

If you have the Signal Processing Toolbox, use the findpeaks function with an approopriate valuee for 'MinPeakProminence' so that it only detects certain peaks —

date = datetime(2022,01,01) : caldays(1) : datetime(2024,9,28);
t = day(date,'dayofyear');
data = cos(2*pi*t/28).*cos(2*pi*t/7)/10+rand(size(date))/10;

[pks,locs] = findpeaks(data, 'MinPeakProminence',0.15);

figure
plot(date, data, '-r','LineWidth',2)
hold on
plot(date(locs), pks, '-k', 'LineWidth',1)
hold off
grid
xlim('tight')
ylim([0 max(ylim)])

You will have to experiment wiith the 'MinPeakProminience' value. A good guess for a starting value is approximately half way between the shortest and tallest peaks, then adjust it as necessary.

It would be helpful to have your data.

[shamal]

thank you but i don't have this toolbox

[Star Strider]

My pleeasure!

O.K. Instead use:

Lvmn = islocalmax(data, 'MinProminence',0.15);

Changing my previous code to accommodate it —

date = datetime(2022,01,01) : caldays(1) : datetime(2024,9,28);
t = day(date,'dayofyear');
data = cos(2*pi*t/28).*cos(2*pi*t/7)/10+rand(size(date))/10;

Lvmn = islocalmax(data, 'MinProminence',0.15);          % Returns Logical Veector
locs = find(Lvmn);                                      % Not Specifically Necessary, Returns Numeric Indices Of Peaks
pks = data(Lvmn);                                       % Necessary, Returns Peak Amplitude Values

figure
plot(date, data, '-r','LineWidth',2)
hold on
plot(date(locs), pks, '-k', 'LineWidth',1)
hold off
grid
xlim('tight')
ylim([0 max(ylim)])

Again, it may be necessary to experiment with the 'MinProminence' value to get the reesult you want.

.

Answer 2

[Walter Roberson]

mask = islocalmaximum(YourSignal);
peak_times = YourSignalTimes(mask);
peak_values = YourSignal(mask);

plot(peak_times, peak_values);