Questions tagged [signal-processing]

Numerical analysis of a digitized signal

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3
votes
1answer
754 views

Peak detection in a ucontroller using FFT

A project I am working on currently is to create a heart beat sensor using a finger plethysmograph. It returns a signal to my ucontoller that only includes positive peaks. For example, the ideal ...
5
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1answer
1k views

Is there an intuitive interpretation of a negative variogram “nugget” value?

A variogram plots the variance of the difference between sample pairs on a field (any dimensionality) against spatial separation (the "lag") of those samples. The extrapolation from observed small-...
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0answers
415 views

On the use of the periodogram of a time series

I have a time series of hourly measurements for a duration of one year: time <- 1:(365*24)/24 set.seed(1) x <- rnorm(length(time)) The measurements are ...
4
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1answer
317 views

Evaluating the variation in the power of a known periodicity

Consider the following example: ...
22
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1answer
22k views

How can I align/synchronize two signals?

I'm doing some research but have come stuck at the analysis stage (should've paid more attention to my stats lectures). I've collected two simultaneous signals: flow rate integrated for volume and ...
5
votes
1answer
1k views

What are some common measures of variation in an interval?

Context: I'm working on an app that "listens" to breathing/snoring and "diagnoses" apnea by taking note of pauses between breaths. For the most part this works well, but it's (rather amazingly) ...
4
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1answer
6k views

How to simulate Signal-Noise Ratio?

I have a vector of simulated data: data = c(0.47, 0.45, 0.30, 1.15, 0.82, 0.38, 0.51, 1.36, 1.72, 0.36) I've been adding noise to this by generating random ...
2
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1answer
793 views

Method to find 'principal components' of EMG recordings of reflexes

I have a series of electromyographic (EMG) reflex recordings, of which I would like to find out the principal components. My thoughts are that there are multiple processes that added together result ...
9
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4answers
13k views

What is a good way to measure the “linearity” of a dataset?

I have an empirically gathered dataset which relates two variables. Over a small range the relationship appears linear, however over a larger range there is clearly some second order polynomial ...
9
votes
1answer
724 views

Techniques for incremental online learning of classifier on stream data

Which may be good techniques to face this abstract problem? You have a data stream of a continuous signal, as one from a physical sensor. That signal has real (discretized) values, no attribute; ...
10
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1answer
902 views

Pattern of mouse (or keybord) clicks and predicting computer user's activity

Based solely on the temporal pattern of mouse clicks (a list of click times $[t_1,t_2,t_3,\ldots]$), is it possible to predict the computer user's activity? For example out of: working vs spending ...
5
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1answer
1k views

Finding the instantaneous period of a signal (or calculating period degradation)

I have a signal, of varying amplitude, and after a certain point in time, I expect to see the period of this signal lengthen. I am looking for a way to measure the lengthening of this period. Is this ...
4
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1answer
3k views

Analysing periodicity in sparse time series

I am interested in looking for periodicities in a several day long recording of electrical activity. The traces present a very steady baseline over which, from time to time, some short events (300-500 ...
1
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1answer
103 views

I need a new and improved DFT

The traditional Discrete Fourier Transform (DFT) and its cousin, the FFT, produce bins that are spaced equally. In other words, you get something like the first 10 hertz in the first bin, 10.1 through ...
10
votes
1answer
714 views

Are MFCCs the optimal method of representing music to a retrieval system?

A signal processing technique, the Mel frequency Cepstrum, is often used to extract information from a musical piece for use in a machine learning task. This method gives a short-term power spectrum, ...
3
votes
1answer
109 views

Three-parts correlation or equivalent?

I'm wondering what's the usual way for detecting "three-parts" association between variables. I'm not even sure about the name, so I apologize for any misunderstandings beforehand. Here is what I want....
3
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1answer
1k views

Wavelet smoothing at different scales

I would like to perform wavelet smoothing at different scales in R. I got the idea from this figure (panel A) were they measure the density/intensity of a particular signal at different scales. Here ...
0
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1answer
758 views

Maximum Likelihood Estimator of SNR for a Known Signal Superimposed in AWGN

Assuming the following model (Fir instant, received signal of a communication / RADAR system): $$ x[n] = \alpha s[n] + w[n] $$ Where: $ s[n] $ is a known signal of length $ L $ and known energy $ p ...
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0answers
115 views

Pattern finding approaches

I'm looking for patterns in a signal. I had used successfully a cross-correlation approach. However, I found some references to Gibbs sampling approaches for finding patterns. My question is: Are ...
2
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0answers
103 views

Detecting the period of a signal with a length of only a few periods [duplicate]

Possible Duplicate: Fourier data with non-integer periods, correcting for phase bias I have a not perfectly but quit periodic signal, with a length of only a few periods. What methods are ...
2
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0answers
646 views

Defining norm of a matrix of MFCC coefficients

Scenario Construction: I have a MFCC generator block which gets the speech samples from the user and generates a rectangular matrix say $A$ of the order $m \times n$, whose elements are the Cesptral ...
1
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1answer
613 views

Do I use non-normalized or normalized fft output from R to compute phase angle?

Is R's fft() output normalized or not? In other words, do I have to normalize the output first before computing the phase angle using ...
3
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1answer
3k views

Characterizing periodicity level of signal

What are some good ways of quantitatively characterizing the periodicity level of an approximately periodic $f(t), t \in \mathbb{R}$ signal? I need this to tell if the output of some system is ...
6
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5answers
6k views

Does PCA have any advantages or usages in the frequency domain?

My question is about analysis of signals with PCA in the frequency domain. As frequency analysis offers a powerful tool for signal processing, does Principal Component Analysis (PCA) have any "well-...
4
votes
1answer
2k views

How can I improve my cross-correlation methodology?

I will break my question appropriately to make it easier to explain. This is actually a short question but looks longer due to my plots so I apologize for that. Any input would be greatly appreciated. ...
3
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1answer
97 views

Finding average settling value after step response

This is crossposted from StackOverflow. Someone suggested I should post it here. Though I don't have enough karma to post images. I'm working with gathering data from a biological monitoring system. ...
2
votes
1answer
581 views

Wavelet analysis of EEG

I want to do a time-frequency analysis of an EEG signal. I found the GSL wavelet function for computing wavelet coefficients. How can I extract actual frequency bands (e.g. 8 - 12 Hz) from that ...
3
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0answers
170 views

A best measure for speaker recognition

I have a set $E_{1}$, with a finite cardinality $n$ of rectangular matrices which contains the useful MFCC coefficients generated from $n$ speech signals. Similary I have a set $E_{2}$ of same ...
5
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0answers
2k views

What is the best way to compare fluctuations of two signals?

I have some data acquired by an acoustic sensor with 1 Hz sampling rate. Due to some inevitable issues, I have some noise in my signal, saying 10% pollution. I'm looking for a reliable method for ...
5
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2answers
2k views

Online method for detecting wave amplitude

I would like to measure the amplitude of waves in a noisy time-series on-line. I have a time-series that models a noisy wave function, that undergoes shifts in amplitude. Say, for example, something ...
6
votes
2answers
487 views

How to average quantized and truncated data?

So I have data that has been quantized by an analogue to digital converter. (continuous data has been turned into discrete data and the values range from 0 to the saturation value , which is 127 in ...
9
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1answer
962 views

Boundary effect in a wavelet multi resolution analysis

What are the methods to minimize the effect of boundaries in a wavelet decomposition? I use R and the package waveslim. I have found for instance the function ...
7
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2answers
258 views

Compression theory, practice, for time series with values in a space of distributions (say of a real random variable)

Example of problem: Part of our research team is working on providing operationally wind power forecast. Usually, since there are different time scalse that interest forecast user, a forecast is ...
4
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1answer
275 views

How would you filter this?

This image show a histogram (200 bins) of accumulated distances from a radar distance meter (very noisy). The peak around 7 meters is an object. At thought this looked kind of like a normal ...
5
votes
2answers
638 views

Generalization of the Signal-Noise ratio for non-Gaussian processes

The signal to noise ratio is simple, and is usually defined in the context of simple Gaussian local-level models. In the cause of non-gaussian signal or noise models, do people do things more ...
7
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1answer
2k views

Using autocorrelation to find commonly occurring signal fragments

I have a sensor which is capturing accelerometer data as a person walks. What I'm interested in extracting is each signal fragment when a step is taken. The Z-axis is what is used since only one axis ...
15
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4answers
4k views

Smoothing time series data

I am building an android application that records accelerometer data during sleep, so as to analyze sleep trends and optionally wake the user near a desired time during light sleep. I have already ...
25
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3answers
11k views

Application of wavelets to time-series-based anomaly detection algorithms

I've been beginning to work my way through Statistical Data Mining Tutorials by Andrew Moore (highly recommended for anyone else first venturing into this field). I started by reading this extremely ...
11
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2answers
3k views

What is the difference between functional data analysis and high dimensional data analysis

There are a lot of references in the statistic literature to "functional data" (i.e. data that are curves), and in parallel, to "high dimensional data" (i.e. when data are high dimensional vectors). ...
10
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6answers
856 views

Dubious use of signal processing principles to identify a trend

I am proposing to try and find a trend in some very noisy long term data. The data is basically weekly measurements of something which moved about 5mm over a period of about 8 months. The data is to ...
6
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2answers
9k views

What's the purpose of window function in spectral analysis?

I'd like to see the answer with qualitative view on the problem, not just definition. Examples and analogous from other areas of applied math also would be good. I understand, my question is silly, ...

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