Effacer les filtres
Effacer les filtres

problem of using findpeaks

8 vues (au cours des 30 derniers jours)
jie hu
jie hu le 28 Nov 2023
Réponse apportée : Chunru le 28 Nov 2023
I have two vectors of time (datetime formate) and elevation, but there is an error to use findpeaks(elev,time), saying "Expected X to be strictly increasing."

Réponses (2)

Star Strider
Star Strider le 28 Nov 2023
My guess is that the datetime values are not considered to be monotonically increasing because they span multiple years.
Try this as a work-around —
LD = load('19year.mat');
elev = LD.elev;
timing = LD.timing;
[pks,plocs] = findpeaks(elev);
[vys,vlocs] = findpeaks(-elev);
figure
plot(timing, elev, 'DisplayName','Data')
hold on
plot(timing(plocs), pks, '^r', 'MarkerSize',2.5, 'DisplayName','Peaks')
plot(timing(vlocs), -vys, 'vg', 'MarkerSize',2.5, 'DisplayName','Valleys')
hold off
grid
xlabel('timing')
ylabel('elev')
legend('Location','best')
figure
plot(timing, elev, 'DisplayName','Data')
hold on
plot(timing(plocs), pks, '^r', 'DisplayName','Peaks')
plot(timing(vlocs), -vys, 'vg', 'DisplayName','Valleys')
hold off
grid
xlabel('timing')
ylabel('elev')
legend('Location','best')
xlim([timing(1) timing(500)])
.

Chunru
Chunru le 28 Nov 2023
load(websave("19year.mat", "https://www.mathworks.com/matlabcentral/answers/uploaded_files/1553817/19year.mat"))
% It seems that timing contains duplcate data.
% fild peaks require x-axis to be monotonically increasing.
% Workaround:
% sort the data
[timing, i] = sort(timing);
elev = elev(i);
% find the peaks and location
[pks, locs] = findpeaks(elev, MinPeakProminence=1);
plot(timing, elev);
hold on
plot(timing(locs), pks, 'rv', 'Markersize', 5)

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