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How to express local peak in Matlab

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Nab

Nab

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plz, can some help me, to experess the local peak in matlab
tnks
 

Local peak in Matlab

Hi
I dont know any simple orders in MATLAB for to find local maxima

but maybe :

FIRST LP YOUR DATA,say D

then:
D=[...] %array of your data
C=der(D) % first derivative of your data
C(C<Th & C>-1*Th)=0 % set zero small values
find(C==0)
the latest order will give you the points in which derivative is zero or small.

1)YOU HAVE TO CHOOSE Th PROPERLY
2)DONT FORGET TO INSERT TIME AS A COPEFFICIENT FOR ABOVE RELATIONS (here dt=1)


3)if your data is parametric (& has a simple relation with time),Symbolic toolbox is capable to do what you want(check DSOLVE & DIFF in sym.tool box)

4)HONESTLY ,THERE SHOULD BETTER WAYS!!
I CANT HELP YOU FOR NOW
regards
Armin
 

    Nab

    Nab

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Re: Local peak in Matlab

thanks, for your answer, but the pb is more difficult,

in the picture there is 2 peak that i want to extract , the 2 peaks that are in the right and left of the graphe, i must have their position , thanks **broken link removed**
 
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Local peak in Matlab

Hi Nab
I will appreciate if you upload a file containing your data.

(you can use this code to generate it):
%--------------------------------
D=[..];% your data
fid=fopenf('file_name','wt') %open file if not
%available make it
fprintf(fid,%d,D) %(?)write data to file
%-------------------------------

well i'm not sure about the last line ,please check it

thanks
wainting for your response

Armin
 

Re: Local peak in Matlab

@Armin, really thnx ,i'm sorry for the delay, so i tested an other methode and it works here the code, thnx again for your aswers :
z=peaks;
z=z(30,:);
d=diff(sign(diff(z)));
j=find(d==-2)+1;
plot(z)
hold on
plot(j,z(j),'r*')
:D

the pb now, is that my signal is an additive gaussiane white noise,,,:cry:
 

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