您正在关注此问题

您将在关注的内容源中看到更新。
您可能会收到电子邮件，具体取决于您的通信预设项。

How to correct for drift in a signal not using detrend

7 次查看（过去 30 天）

显示更早的评论

Rebecca Ellis 2018-10-2

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend

⋮

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend

编辑： dpb 2018-10-2

image.png
image.png

在 MATLAB Online 中打开

I have a 30 hour data set, where I am interested in taking out the drift the last 10 hours of the dataset. It is very important to keep the dataset at the same length as I started as I have other sensors in the system that I am looking at with this signal. I have tried:

sdata = oxygen_unisense.data;
oxygen_unisense.detrend = detrend(sdata(3.715958429982246e+06:end));
 oxygen_unisense.mean = oxygen_unisense.data - oxygen_unisense.detrend;

but this puts the part of the signal to zero.

Anyone with suggestions?

Data: https://www.dropbox.com/s/c8uy84e2ndem1nl/oxygen_unisensemathelp.mat?dl=0

12 个评论
显示 10更早的评论隐藏 10更早的评论

Rebecca Ellis 2018-10-2

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616651

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616651

在 MATLAB Online 中打开

lf = polyfit(oxygen_unisense.time(3715958.429982246:end),oxygen_unisense.data(3715958.429982246:end),1);
plot(oxygen_unisense.time(3715958.429982246:end),oxygen_unisense.time(3715958.429982246:end)*lf(1) + lf(2),'--k');
plot(oxygen_unisense.time(3715958.429982246:end),oxygen_unisense.time(3715958.429982246:end)*-lf(1) + oxygen_unisense.data(3715958.429982246:end))
trying this aswell

dpb 2018-10-2

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616653

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616653

编辑：dpb 2018-10-2

You'll have to be able to find the breaks in the signal at the points of interest first.

Then, just detrend that section and substitute that result into the overall signal at that location in the original.

ADDENDUM

You'll have to do something about adjusting level to keep continuity at the breakpoint, however...

Alternatively, just return the slope from linear fit and adjust the portion by the ratio it would return should do it.

Rebecca Ellis 2018-10-2

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616847

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616847

Thank you for your reply, what would the code be for this? The points if interest are (3.715958429982246e+06:end). Would the polyfit function work?

jonas 2018-10-2

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616896

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616896

You could also use findchangepts to segment the entire signal and detrend each segment individually

Rebecca Ellis 2018-10-2

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616911

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616911

编辑：Rebecca Ellis 2018-10-2

I only want to change one part of the data (The point of interest = 3.715958429982246e+06 to the end. It is drifting linearly.

dpb 2018-10-2

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616920

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616920

在 MATLAB Online 中打开

I don't understand what that means, precisely, then.

|detrend| doesn't "zero", it removes linear trend unless use the optional 'constant' argument with which it simply subtracts the mean.

The 'linear' option is default; I'd forgotten but actually you can specify breakpoints with default as written which should just be "the cat's meow" once you identify the section(s) of interest.

jonas 2018-10-2

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616927

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616927

@Rebecca: 3.715958429982246e+06 is not a valid index (although MATLAB seems to round it automatically)

Rebecca Ellis 2018-10-2

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616931

⋮

链接

此评论的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/421711-how-to-correct-for-drift-in-a-signal-not-using-detrend#comment_616931

在 MATLAB Online 中打开

image.png

sdata = oxygen_unisense.data;
sd=sdata(3.715958429982246e+06:5.838709e6); %Take a section of interest
Hz=64;
%Filter the data to lowpass filter it
b = ones(1,(round(Hz*1000)+1))/(round(Hz*1000)+1);
filtdat=filtfilt(b,1,sd); % This takes a while.
%Substract the filtered from the original signal
sdff=sd-filtdat;
figure
subplot(2,1,1)
plot(sd)
hold all
plot(filtdat)
xlabel('Datapoint')
ylabel('Data')
legend('Original Data','Filtered Data')
subplot(2,1,2)
plot(sdff)
xlabel('Datapoint')
ylabel('Data')
oxygen_unisense.data(3.715958429982246e+06:5.838709e6) =sdff;