how to isolate harmonic component from figure

Dear all ,

If I have a signal with harmonic how can I automatical know the index (the position of each number of the harmonic) . In another way , I need to know when the harmonic happens.

The data are in the attachment file

Answer 1

[Simon Chan]

Try the following to see whether this is what you want or not.

clear; clc;
load('xx.mat');
x = 1:length(xx);
% Separate entire signal into 3 sections
upperTh = 0.95*max(xx);
lowerTh = 0.95*min(xx);
index = xx<upperTh & xx>lowerTh;
istart = find(diff(index)==1);
iend = find(diff(index)==-1);
profile = arrayfun(@(r,s) xx(r:s),istart,iend,'uni',0);         % 3 separate profiles
% Determine the positions of the turning points
[~,idx1] = cellfun(@(x) min(diff(diff(x)>0)),profile);
[~,idx2] = cellfun(@(x) max(diff(diff(x)>0)),profile);
rangeIdx = sort([idx1, idx2],2) + istart;
% Adding some offset besides turning points to find min/max
offset = 5;
harmonic = arrayfun(@(r,s) xx(r-offset:s+offset),rangeIdx(:,1),rangeIdx(:,2),'uni',0);
[maxValue,maxIdx] = cellfun(@max,harmonic);
[minValue,minIdx] = cellfun(@min,harmonic);
% Plot result only (Can be ignored)
for k = 1:3
    subplot(3,1,k)
    plot(x(rangeIdx(k,1)-offset:rangeIdx(k,2)+offset),harmonic{k});
    title({sprintf('MinValue = %.4f, MinPos = %d',minValue(k),rangeIdx(k,1)-offset+minIdx(k)-1);...
        sprintf('MaxValue = %.4f, MaxPos = %d',maxValue(k),rangeIdx(k,1)-offset+maxIdx(k)-1)});
    grid on
end

[Hassan Abdelazeem]

Thank you for your code, it was really geat but maybe I am not so clear enough

what exactly I need to do is , if I have a hystresesis loop and there are harmonics i need at this harmonic do another action

load('m3rdr.mat')
x=m3rdr(:,1);y=m3rdr(:,2);
plot(x,y)

[Simon Chan]

Use another approach to retrieve the positions of the hystersis loops as follows.

After that, you can use the start and end position index for further actions.

clear; clc;
load('m3rdr.mat');
xx = m3rdr(:,1);
yy = m3rdr(:,2);
% Extract the holes from the polygons
pgon = polyshape(xx,yy);                % Build the polyshape, ignore the warning

Warning: Polyshape has duplicate vertices, intersections, or other inconsistencies that may produce inaccurate or unexpected results. Input data has been modified to create a well-defined polyshape.

polyout = holes(pgon);                  % Extract holes which are the hystersis loops
figure
subplot(2,2,1)
plot(pgon);                             % Display original signals
ax1 = gca;
title('Original shape');
xLimit = ax1.XLim;
yLimit = ax1.YLim;
grid(ax1,'on');
subplot(2,2,2)
plot(polyout);                          % Display the extracted holes
ax2 = gca;
title('Extract holes coordinates');
ax2.XLim = xLimit;
ax2.YLim = yLimit;
grid(ax2,'on');
for k = 1:length(polyout)
    subplot(2,2,k+2)
    % Start position of the extarcted hole
    xstart = polyout(k).Vertices(1,1); 
    % End position of the extarcted hole, the last vertice is not used
    xend = polyout(k).Vertices(end-1,1);        
    startIdx = find(xx == xstart);
    endIdx= find(xx == xend);
    plot(xx(startIdx:endIdx+1),yy(startIdx:endIdx+1));
    hold on
    grid on
    plot(xx(startIdx),yy(startIdx),'g*');   % Start point showing green dot
    plot(xx(endIdx+1),yy(endIdx+1),'r*');   % Last point showing red dot
    title({sprintf('Start Position = %d',startIdx);...
        sprintf('End Position = %d',endIdx+1)});
    hold off
end