selection of specific data from graph and extract data
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%For given graph only peck values between 10 and 20hz is valuble and i like to extract phase value for specific point.
%Right now my peck function is taking all the small changes, is there any way i can pass some filter or anything?
%Code:
header = 9;
delimiter = '\t';
ind = 1:100;
for i = 1:4
filname = sprintf('H1, 2_I1sv%05d.txt',i);
dat(i) =importdata(filname,delimiter,header);
FRFdata = dat(i).data;
f = FRFdata(:,1);
a = FRFdata(:,2);
b = FRFdata(:,3);
amp = sqrt(a.^2 + b.^2);
pha = (180/pi)* atan2(b,a);
[Ypk,Xpk,Wpk1,Ppk] = findpeaks(amp(ind));
figure(i)
subplot(2,1,1),plot(f,amp,f(Xpk),Ypk,'dr')
grid on
ylabel('Amp')
xlim([0 40])
ylim([0 2.4])
subplot(2,1,2),plot(f,pha)
grid on
xlim([0 40])
xlabel('Hz')
ylabel('Phase')
end
%I am doing FRF analysis to find vibration modes
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Accepted Answer
Star Strider
on 14 Mar 2023
The findpeaks function has a number of name-value pair arguments that can be used to return only selected information.
See if:
[Ypk,Xpk,Wpk1,Ppk] = findpeaks(amp(ind), 'MinPeakProminence',0.5);
does what you want.
I also tweaked your code a bit to make it abit mor efficient, specifically using readmatrix and changing ‘amp’ and ‘pha’
header = 9;
delimiter = '\t';
ind = 1:100;
i = 1;
% for i = 1:4
% filname = sprintf('H1, 2_I1sv%05d.txt',i);
filname = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/1323755/H1,%202_I1sv00001.txt';
% dat(i) =importdata(filname,delimiter,header);
FRFdata = readmatrix(filname, 'HeaderLines',9);
% FRFdata = dat;
f = FRFdata(:,1);
a = FRFdata(:,2);
b = FRFdata(:,3);
amp = hypot(a,b); % Changed
pha = atan2d(b,a); % Changed
[Ypk,Xpk,Wpk1,Ppk] = findpeaks(amp(ind), 'MinPeakProminence',0.5); % Changed
figure(i)
subplot(2,1,1),plot(f,amp,f(Xpk),Ypk,'dr')
grid on
ylabel('Amp')
xlim([0 40])
ylim([0 2.4])
subplot(2,1,2),plot(f,pha, f(Xpk),pha(Xpk),'dr') % Changed
grid on
xlim([0 40])
xlabel('Hz')
ylabel('Phase')
% end
.
7 Comments
Star Strider
on 15 Mar 2023
As always, my pleasure!
It appears that you got everything working the way you want!
sgtitle("File: H1, 2\_I1s" + i + "v.txt")
.The backslant (\) is necessary to ‘escape’ the underscore so that it prints as an underscore and does not subscript the ‘I’ that follows it.
.
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