Finding minima
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I have a data file with few valleys (minima). is there a way to find all the x coordinates corresponding to each minimum y value?
采纳的回答
Matt Tearle
2011-2-15
If you want fancy, take Walter's advice and search FEx. If you want quick and dirty:
x = 1:50;
y = sin(5*x);
idx = [false, y(3:end)>y(2:end-1) & y(2:end-1)<y(1:end-2), false];
xmin = x(idx)
plot(x,y,'o-',xmin,y(idx),'rx')
7 个评论
Walter Roberson
2011-2-15
The above code unfortunately picks up on every local valley; the contributions in the FEX worry about noise and defining how much of a change there can be before saying that one has entered a new extreme or if two adjacent extreme should be considered part of the same series or not...
Matt Tearle
2011-2-15
Right, that's why I said "quick and dirty"
Paulo Silva
2011-2-15
Matlabs findpeaks will do the job just fine, the recent matlab version have a better implementation of findpeaks.
Matt Tearle
2011-2-15
True, but note: FINDPEAKS is a Signal Processing Toolbox function.
Paulo Silva
2011-2-15
Matt your simple detection is very interesting :) I never thought about it that way, it's not perfect but might be very useful, thanks for sharing it.
Matt Tearle
2011-2-16
Hah. Actually I just hunt the intartubes looking for places to apply logical indexing! ;)
Paulo Silva
2011-2-16
Here's my 1 vote :)
更多回答（3 个）
Walter Roberson
2011-2-15
0 个投票
There is are a fair number of postings, and several Matlab File Exchange contributions, for finding peaks, which you could either modify or apply to the negative of your data.
Andrew Newell
2011-2-15
0 个投票
Graig
2011-2-15
0 个投票
1 个评论
Matt Tearle
2011-2-16
To help others who might have the same question, it would be great if you could vote for and/or accept answers that you think should be given prominence. Thanks.
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