Finding peaks and troughs of sinusoidal from a Matrix and elements bounded within

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Nkenna Amadi 2018-7-3

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https://ww2.mathworks.cn/matlabcentral/answers/408589-finding-peaks-and-troughs-of-sinusoidal-from-a-matrix-and-elements-bounded-within

编辑： jonas 2018-7-4

Hello i have a matrix that consists of zeros and ones. It has 5 sinusodial shapes linked together as seen in the image attached. The yellow represents where the value of the matrix is one and the blue for zero. How do i find the peaks and troughs of each of this sinusodial shapes and the indices/elements(rows and columuns) bounded by each of these sinusodial shapes. Basically i should have something that gives the peak and trough for sinusodial one and then the elements within it

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jonas 2018-7-3

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编辑：jonas 2018-7-3

在 MATLAB Online 中打开

untitled11.jpg

Since you did not attach the data, I had to start from your attached image. Therefore my x- and y-values are not scaled correctly. Basically you get the coordinates with find() and then findpeaks() to locate peaks and troughs. See attachment for results.

%%Fix binary image
RGB=imread('pic.png');
GRAY = rgb2gray(RGB);
threshold = graythresh(GRAY);
BW = im2bw(GRAY, threshold);
%Crop edges
BW=BW(5:end-10,60:end-30);
imshow(BW)
%%Find coordinates of ones
[y,x]=find(BW==1)
%%Find peaks and troughs
[~,locs1]=findpeaks(y.*-1,'minpeakprominence',20,...
    'minpeakdistance',50)
[~,locs2]=findpeaks(y,'minpeakprominence',20,...
    'minpeakdistance',50)
%%Plot data
figure;
plot(x,y,'-',...
    x(locs1),y(locs1),'-x',...
    x(locs2),y(locs2),'-x')