Unanswered Questions
4,521 questions with no upvoted or accepted answers
11
votes
0answers
675 views
Will an Unscented Kalman Filter Be “As Good” as Other Optimization Algorithms for This Problem?
I want to calibrate a tri-axis magnetometer when a tri-axis gyroscope is also available.
I am fairly certain I can solve this problem using various optimisation algorithms, but I would prefer to use ...
10
votes
0answers
1k views
Ensemble learning, multiple classifier system
I am trying to use a MCS (Multi classifier system) to do some better work on limited data i.e become more accurate.
I am using K-means clustering at the moment but may choose to go with FCM (Fuzzy c-...
9
votes
3answers
14k views
First order low pass filter
I am trying to better understand the first-order low pass filter:
Summary:
Per wikipedia, a first order low pass filter yields the following in discrete time:
$$
\frac{Y(s)}{U(s)}= \frac{\omega_{c}}...
9
votes
0answers
1k views
Help in Retraining a HOG Descriptor using SVMLight
I am currently trying to count cars using OpenCV 2.4.4 with a HOG descriptor. Because a model for car detection is not available in OpenCV, I am creating my own model using SVMLight and a dataset of ...
7
votes
1answer
263 views
What's the similarities and differences between Wigner transform and wavelet transform?
Wigner transform and continuous wavelet transform are both some kind of time-frequency representation of a signal. What are the similarities and differences between them? Could you give some ...
6
votes
0answers
88 views
Converting very short “motionless” video frames to single, better-resolved, images
I made a mistake with my newly bought compact camera, before a trip to Japan. Instead of taking single pictures, I ended up with a few short "MP4" video files (1 second, 2-3 frames). I could ...
6
votes
1answer
1k views
Issues with the smoothing operator in coherence estimation using the complex Morlet (Gabor) wavelet
The goal
I wish to compute the coherence estimate using the continuous wavelet transform (CWT) of a real-valued signal with the complex Morlet (a.k.a. Gabor) wavelet. I compute the cwt of the signal ...
6
votes
2answers
480 views
Efficient calculation of correlation function every $N^{\rm th}$ point
I would like to calculate a long correlation function of length say, 1e6 points.
I have a prior knowledge that the correlation peak will be in point k*1000.
Is there an efficient way to apply this ...
6
votes
1answer
281 views
Analytical Expression for Convolution of Two 2D DFTs
I am trying to do an image analysis problem on some images, and I want to calculate some things in the frequency domain which are giving me problems. Say I have an (discrete) image $I(x,y)$ of size $...
6
votes
3answers
3k views
Filter size vs. FFT size and Overlap add
First of all I would like to say that :
I'm new to DSP and in a "learning curve" hence the "basicness" of my questions.
I've read as many posts/articles as possible on the ...
6
votes
2answers
393 views
Deconvolution Question on Article “Deriving Intrinsic Images from Image Sequences” by Yair Weiss
there are n derivative filters: $f_i$, and denote $f_i^r$ as $f_i$'s reverse filter such that
$$f_i(x,y)=f_i^r(-x, -y)$$
$r_i, f_i$ given, to find $r$ from the equations:
$$f_i * r = r_i, (1 \leq i \...
6
votes
0answers
179 views
EWMA based differential that is strictly positive on strictly increasing irregular time series?
Let's say I have a time series $ \{t_i, x_i\} $ where the $x_i$ are strictly increasing and the $t_i$ are not regularly spaced. I can define a differential operator as
$$ \Delta_i = \frac{x_i-x_{i-1}...
6
votes
1answer
233 views
Regarding the choice of cost function in adaptive control - squared error vs absolute error
I did search the question database regarding this question, and although one or two questions came close, they didn't really address my specific question.
In adaptive control based on minimizing ...
6
votes
1answer
876 views
How to choose a windowing function when performing a Chirp $\mathcal Z$-transform?
I've got some data sampled at 32 Hz. The only interesting stuff is happening between about 0-8 Hz and I've got to do real time batch processing and detect events with a delay of no more than a second. ...
5
votes
0answers
160 views
Residual error when setting measurement matrix in compresssive sensing
I have an issue when implementing compressive sensing to recover sparse vector. Assume I have sparse vector $x$ of length, for example, $(256,1)$. $x = [x_1,x_2,.....x_{256}]$. This vector is ...
