Identifying certain x value of a graph when x is not dependent on y?

Hi, I have plotted 2 columns of data from an excel sheet, I have identified several peaks and I would like to know the times associated with these peaks without just zooming in on each value. Basically is there a way to extract an x value given the graph, even though the x and y values are independent?

Similar code would be;

Time = xlsread('Data.xlsx', 'C2:C5000');

Time = Time/500;

Activity = xlsread('Data.xlsx', 'E2:E5000');

FilterActive = sgolayfilt(Activity, 5, 9); % can be removed

peaks = findpeaks(FilterActive, 'MinPeakHeight', 0.4);

plot(Time, FilterActive)

Im very new and inexperienced with coding, so any help or suggestions are welcome and appreciated, thanks.

Answer 1

[Star Strider]

Ask for a second output from findpeaks.

If you want the indices of the peaks, just use:

[peaks, peak_loc_idx] = findpeaks(FilterActive, 'MinPeakHeight', 0.4);

The ‘x’ values (in the actual units of ‘x’) will then be:

xval = x(peak_loc_idx);

corresponding to the ‘x’ value at each peak.

There are other ways to get the ‘x’ values directly. See the documentation for findpeaks for details.