I am working with sensor signals and finding some problems with signal manipulation .(Any idea /hint /suggestion are welcome as i need something to move forward .
I have chnaged the qurey and added some new and more details to make the question easy to understand.
I have 2 signals.
⦁ Light Pink is the original Signal (refernce signal)with Red dots showing Local maxima’s.
⦁ Blue is a signal which is found after having test from another sensor that looks like refernce sensor but have some faults in it as it is made by us.
⦁ These signals are plotted against time on x-axis.
I have attached some plausible / some part of values of signal here so if anyone can help me with the logic along with MATLAB code it will be of great help.
⦁ Please open the attached link .
⦁ Copy the code written in MATLAB and run after saving it .
⦁ You will see 2 signals as shown in figure and when u will zoom it you will clearly see the difference.
(How to make my Original signal Pink signal Straight as like blue signal in plots)
Question:
⦁ I want to make my original signal (pink) to look alike blue signal interms of flat portion only.
Common behaviour to observe the logic:
⦁ The common behavior that I have seen in my measured signal is that it gets flat where it finds local maxima (either on positive side or negative side).
⦁ At every point in local maxima I see that my blue signal gets flat.
Everything I have to do is with Original signal (Pink signal) to formulate some results.
Is there any way, I can make my original signal flat just like blue signal.
Can someone suggest me the best way to do that? And some one provide me an example MATLAB code then it would be great help .
Please have a look at the picture to get a glimpse about my idea.
Thanks a lot in adavance for help.
I have tried few techniques.
The results of those Techniques are as follows but speaking truly nothing is working for me uptill now.
I have find local maxima values and using nlfilter applied neighborhood rule and tried to make the peaks and neighborhood area flat but unfortunately it is not working as window size is fixed but in my case window size varies and it also depends upon position of local maxima and most important constant window size changes the shape of the signal.
I have also tried to apply varying window but its not working for me may be i have not good concept of how to apply varying size window. I do not know how it will work for my signal.
Cut the long story short what I have done up till now is not working so I need help in that.
It will be really nice if someone provides me how to solve this issue and If i will get some MATLAB so it will great for me.
Thanks a lot in advance for your time ,expertise and help.
Code for running the variables of data in the attached Link:
load originalflatenninrough t original_signal_data measured_Signal_data
[p l] = findpeaks(original_signal_data);
[pn ln] = findpeaks(-original_signal_data);
figure(1)
hold on
plot(t,original_signal_data,'m')
plot(t,measured_Signal_data,'b')
plot(t(l),p,'ko','MarkerFaceColor','r');
plot(t(ln),-pn,'ko','MarkerFaceColor','r');
legend ('originalsignal', 'measureddatasignal')
hold off
Code on Test data example data for NL filter (Which is applied on original signal)
n = 10; % number of values to replace in the neighborhood of a local max
t= 0:0.001:10;
A = sin(2*pi*t);
[pks,locs] = findpeaks(A);
% [pks,locs] = findpeaks(-A);
locs = (locs) ;
locations = zeros(size(A));
locations(locs) = true;
locations = conv(locations, ones(1, 2*n+1), 'same') > 0;
X = -inf(size(A)); % create temporary
X(locs) = A(locs); % copy the local maxima
X = nlfilter(X, [1 2*n+1 ], @(x) max(x)); %replace all values with it local maxima
X(locs) = A(locs); % ensure local maxima are not changed
A(locations) = X(locations); % copy filtered temporary to output
figure()
hold on
plot(t,A,'b')
A = sin(2*pi*t);
plot(t,A,'g')
https://www.mediafire.com/folder/7720j3w7b8pj4/Internet_files
Somehow it is not clear to me..are u saying that original signal (supposed to be independent/input ) should be changed to look alike measured signal (dependant on input ). What is the function you used in nlfilter? Anyways seems like u need some sort of regression learning technique.
I agree with Mrinmoy above. What you are trying to do sounds strange: Make the independent variable (the original signal) resemble the dependent signal (measured signal)? I dare say that it sounds rather like an accountant trying to somehow cheat on cost reporting, for which elegant rules are unlikely to be found. Presumably there is come confusion in the posing of the question.
Ronald
Thanks a lot Mrinmoy Sandilya for having a look at my question.
Actually I want to make my original signal flat at points my measured signal is flat.
Original Signal is Refernce signal Data and measured signal data is calculated from signal that is made by us it looks like refernce signal but have some differences that you can see in figure.
The major difference is that my measured signal is flat at points of local maxima.
I am trying to make a model and for that I am trying to make my original signal flat at points of local maxima just like measured signal(blue signal).
Regarding NL filter I have uploaded the code also . I have applied NL filter on original signal and what it does. Code find local maxima and through NL filter I have tried to assign the neighbours same values as of value of local maxima to make it flat but only problem in this is that NL filter makes a fixed window with fix width but as you se in figure and from my attached signal data that my flat part in a signal is not fixed and also position of local maxima is not fixed .
Means at some peaks there are less values at left side of local maxima than right side so fixed width window will not work better in this case. Thats why i am finding some solution to solve this issue.
You have mentioned Regression technique . Can you please eplain shortly or with some example that how it will work because my original signal contains more values so i have to lessen the values but not through desampling . The reason is that I only want my original signal to behave similar to measured signal at flat parts not on other areas.
Please let me know if i remained able to clarify my idea to you.
Thanks a lot in advance for your time .
Dr Ronald Kessel Thanks a lot for stopping by my question. Sorry may be the clarification of my question was not upto the mark. Actually I have a lot tests data sets for sensors that we made and we are trying to make a model and we want to check out what are the changes that have occurred in my measured signal from reference (original)signal. Yes i am trying to do reverse engineering for verification of my calculation of errors in a signal. This is the reason I am trying to make my original signal (Flat )at points where my measured signal is flat and there are some other factors involved but i have calculated those. I hope i remained able to clarify my idea to you.
(the original signal) This is just a reference signal measured from some sensor (which is giving some accurate results) and the (measured signal) is taken from some other sensor which is after tests drives so both signals are different. Take an example of Carbon its standered and we match the other values with carbon.
I was thinking of some kind of curve fitting with least squares you know. Like at each point it will find the residue (perpandicular offset) between measured data (since you have mesaured data points which you used to find out the measured data curve) and original signal and try to minimize the residue. This regression technique may help you find a match between original and measured data. Anyways you have both data sets so you can tune/modify either of it to the other. However the method will be non-linear regression since only those data points are to be changed where measured data is flat.
http://mathworld.wolfram.com/LeastSquaresFitting.html
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