MATLAB: How to find a slope of signal if we do not know the value of x1, x2, y1, y2

signalslope

How can we find the slope of a signal if we do not know the value of x1, x2, y1, y2

which we cannot use

Slope = (y2 - y1) / (x2 - x1);

Example:

load sunspot.dat
year = sunspot(:,1);
avSpots = sunspot(:,2);
[pks,loc]=findpeaks(avSpots,year, 'Annotate','extents','WidthReference','halfheight')
axis([1700 1711 0 100])

give a graph of

Thank you

Best Answer

I am not certain what you intend by ‘slope of a signal’. You can easily determine the derivatives of the signal with the gradient (link) function.

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MATLAB: How to find peaks for a graph plotted in semi-log axes and to extract the values of peak and FWHM

Use findpeaks with more than 2 outputs:

[pks,locs,widths,proms] = findpeaks(PeakSig,x);

See the documentation section on Peak Prominences (link) for details. It specifically describes the ‘widths’ output as ‘Display the prominences and the widths at half prominence of all the peaks.’

MATLAB: How to cut out specific segment from findpeaks function

You can get the ‘Borders’ x-coordinates using:

(Previous Code)
findpeaks(PeakSig,x,'Annotate','extents','WidthReference','halfheight')
title('Signal Peak Widths')
Ax = gca;
Kids = Ax.Children;
Borders = Kids(1:2);
Line = Borders.XData;

You have to search the ‘Axes.Children’ result manually to find the ‘(Border)’ elements. There appears to be no way to get them automatically, or even to specifically search for a ‘Line (Border)’ or ‘Border’ entry in the ‘Kids’ variable. (There may be a way, but it would take more patience than I have tonight to find it. I’ve tried every cell and structure addressing approach I can think of or can find in the documentation, including using strcmp and related functions, and couldn’t get a good result.) It would be very nice if this was more straightforward.

Best Answer

Related Solutions

MATLAB: How to find peaks for a graph plotted in semi-log axes and to extract the values of peak and FWHM

MATLAB: How to cut out specific segment from findpeaks function

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