MATLAB (MATrix LABoratory) is a numerical computing environment and a fourth-generation programming language. Use this tag with care.. see excerpt.

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15 views

Removal of skull stripe from MR image

How to remove the skull stripe from an MR image and to get the csf part from the image clearly? ...
0
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0answers
19 views

How to display images with log axes?

I'm trying to plot few points on existing log-log graph, for comparison. I've saved the existing graph as .png image then I plotted the points on the image!. The difficulty I'm having is how to ...
0
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0answers
7 views

Inverse Distance Weighting Filter

I am trying to use “inverse distance weighting” to improve on some 2D map (called B1-map in MRI field). I am generating this map on voxelwise basis. My algorithm returns the value right most of the ...
0
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0answers
29 views

What is the best method to estimate the frequency(PSD) for noise signal

I’ve been trying to estimate the frequency of a signal I obtained at 1000Hz sampling frequency. The dominant frequency is expected to be not more than 4 or 5 Hz. I’ve estimated the PSD using ...
2
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1answer
40 views

Bicubic Interpolation

I'm trying to do bicubic interpolation on an 8*8 matrix(image) shown below. ...
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0answers
21 views

Linear time-invariant time response kernel, MATLAB vs Octave

I am trying to get some MATLAB scripts to run in Octave, but have a problem with the following line of code: x = ltitr( a, b, u, x0 ) ; which throws an error in ...
0
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1answer
68 views

Solution to Cross-correlation problem of 2 audio signals

There are 2 audio signals, X & Y. X is of 15 second duration. The duration of Y is not given. Y is a part of signal X (ie a small part of audio X is extracted & made into audio Y) I have to ...
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1answer
15 views

any in built function to read a part of an image in malab? [on hold]

i am dealing with images with size 6000x9000 (16 bit). if i want to perform any mathematical operations on whole image it takes lot of time,at the same time it consumes a lot of working memory.i want ...
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3answers
56 views

Appying a Filter Several Times on Data

I have data from an experiment and apply a lowpass filter (digital Butterworth filter, in Matlab). My question ist what happens if I apply the same filter e. g. 2 times on the data? What is ...
0
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0answers
10 views

Process Noise “Q” covarience matrix in a kalman filter

I am trying to implement a Kalman filter on a Phasor Measurement Unit (PMU) values. I meaured the signal from PMU and give those meaurement as input to Kalman filter to get best estimate. I do not ...
0
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0answers
21 views

Detecting white noise signal and narrowing the frequency in matlab

I created a white noise that is played in 2 channels. While the left channel is active the right is silent and vice versa. I am trying to detect the signal arrival time after it has run through the ...
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0answers
26 views

Window function applied to frequency domain signal - why not to time domain signal? [closed]

How to apply the Hamming window function to FM signal to generate a sweep signal? Here I have wrote the MATLAB program without using chirp function.
2
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1answer
75 views

Compare Overlapping FFTs to a longer FFT

How would you compare the SNR gain from a longer FFT (more samples) to overlapping FFTs? Given the choice, which one would you pick and why? Update: Suppose you have 2048 samples of a signal. ...
0
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1answer
20 views

Determining effect of powers of DFT matrix conjugate on input without multiplying

Suppose I have a DFT matrix $F$ of dimensions $N \times N$ where $N$ is a power of $2$. I convert it into a unitary matrix $\displaystyle U = \frac{F}{\sqrt{N}}$ and compute $S = U^* U^* $. $S$ ...
0
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1answer
24 views

The error between the theoretical value and the simulation value of imaginary part of the FFT results

As we know, a complex analytic signal can be obtained through Fourier transformation of a real value function, and the imaginary part can be reconstructed by Hilbert transform of real part. But I have ...
0
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0answers
10 views

choose correct variant of signal/noise ratio calculation

let us consider following sinusoidal model ...
0
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1answer
56 views

Check for time invariance of a _system_ using MATLAB?

I am having difficulty in developing an algorithm for checking if a given system is time invariant or not. For example, let there be 2 systems with input output relation given as: $$y(t)=x(t-2)$$ ...
0
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1answer
64 views

Calculating power and energy of a signal in matlab

I am a little new to matlab and would like to get some help on how to write a program or a function that can calculate the energy/power of a signal depending on whether the signal is an energy or a ...
2
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1answer
74 views

O(1) peak segmentation algorithm in matlab?

I have an intensity image, similar to the image below. I would like to very quickly, segment this image, into separate peaks. Where each peak is labelled, and segmented. A notional segmentation of ...
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0answers
88 views

Extraction of veins from sclera image

I want to extract sclera blood vein feature: from the sclera image for human identification. Which process should I follow? I already used the Gabor filter with Gabor features and Gabor filter ...
2
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2answers
91 views

Calculation of sampling rate and its effect on an Image?

I know that for a given signal, the sampling frequency $F_s$ must be twice or more than maximum frequency of the signal $F_m$. It is easy to understand the concept for a 1D signal. But I don't know ...
1
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1answer
60 views

Simple fft to Gaussian pulse with MATLAB

trying simply to create femtosecond pulse in MATLAB exactly like in the attached image, the carrier frequency is around 374THz, and my sampling frequency is 10 times the carrier. The results of ...
0
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0answers
68 views

Why does a phase shift in the frequency domain not produce a time delay in the time domain?

Suppose I have an input signal which represents a vehicle front suspension response that has been measured using an accelerometer. It is seen that the measured rear suspension response is effectively ...
0
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0answers
17 views

Issue in partial correlation

For a time series I wanted to plot separately the partial auto correlation. Below is the graph for MA model that I want: This shows plot of two time series of two time series - one is a sequence ...
0
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0answers
34 views

Instantaneous power estimation by discrete hilbert transform - how far does it smooth?

In my research area, instantaneous power in a specific frequency band is commonly estimated by the following procedure: Apply a bandpass filter on the raw signal (e.g. 80-90Hz bandpass). Estimate ...
0
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1answer
27 views

How to change the start point of resampling process?

I'm trying to resample a digital communication signal in SciPy or Matlab. Suppose the signal was sampled at 3 samples per second, and I want to resample it to 2 samples per second, the thing is I also ...
0
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0answers
28 views

How can I simulate a broadband ultrasound transducer in Matlab?

I am using a Matlab model to send a broadband acoustic pulse across a fluid. The centre frequency should be 50kHz with 100% bandwidth. It has been suggested that I apply a window the pulse to ...
0
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1answer
51 views

map two RGB images in Matlab

I wonder is there any algorithm or method that I can map two RGB images together in Matlab. I mean assume I have following images Is there any way I find what number I should multiply each ...
0
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1answer
46 views

Fixed SNR with unitary noise variance

I've just one question : How can I write a model like y = x + w,( with w a white gaussian noise) with a fixed SNR and a noise variance equal to 1. What coefficient may I have before x ? Thanks !
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2answers
126 views

Plotting Real Amplitude of Sine Wave in FFT

Consider a sine wave having an amplitude of 9 and a frequency of 0.3 Hz. I wish to perform an fft and plot the frequency on the x-axis and the real amplitude (i.e. 9) on the y-axis. I am using the ...
0
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0answers
41 views

Issue in crest factor

From Wikipedia: Crest factor is a measure of a waveform, such as alternating current or sound, showing the ratio of peak values to the average value. It is the ratio of peak amplitude of the ...
0
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1answer
45 views

Matlab FFT keeps plotting mirrored values

My Matlab FFT plot keeps showing the mirrored values of my frequency of interest. In this example I am looking for 250Hz with a 3200Hz sampling freq. The FFT plots my value at 266Hz as well as 1330 ...
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0answers
50 views

Why is level of power spectrum dependent on FFT resolution?

I created a sinusoidal wave in some noise, and plotted the power spectrum of the signal using two periodogram estimates (welch procedure). One estimate is 'high resolution' - i.e. it uses a longer ...
1
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1answer
57 views

How to reconstruct the signal which is subjected to FIR filtering - Matlab

I have a signal $x$ which is corrupted by Gaussian noise. The signal $x$ is convolved with a filter with coefficients $h = [1, -2, 1]$, to generate signal $y$. Now the signal is taken to Discrete ...
0
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2answers
42 views

2D-otsu algorithm in Digital image processing

I'm working on image project using Matlab & I heard about 2D-otsu algorithm as effective segmentation with low SNR and low contrast images, but I can't find enough information about it or how to ...
1
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0answers
46 views

Ways to find three curves from palm image

I am asked to extract three curves from palm images. original image expected result. The curves has lower intensity than ...
0
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1answer
60 views

Generating a Sine Signal (for example a voltage sine wave) with changing frequency and changing sample rate (time)?

i have a measured signal (e.g. voltage sine wave) and i would like to generate a sine wave which matches this meausred signal (with the generated sine wave i remove the harmonics from my measured ...
0
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0answers
14 views

sine signal-->gaussian noise-->fading channel for SNR analysis

I'm new to matlab and need some help. I have a project whereby i want to to analyse the SNR of a sine signal which passes through an Additive White Gaussian Noise (simulating weather conditions) and a ...
1
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1answer
34 views

How to average coherences estimated using Welch's method in MATLAB

I'm trying to estimate the average coherence of discontinuous snippets of a signal in MATLAB. For Welch's spectrum estimates, the following works: ...
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0answers
12 views

Generating a Sine Signal (for example a voltage sine wave) with changing frequency and changing sample rate (time)? [duplicate]

i have a measured signal (e.g. voltage sine wave) and i would like to generate a sine wave which matches this meausred signal (with the generated sine wave i remove the harmonics from my measured ...
0
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1answer
37 views

Basics of waveform, how to define the zero point

Audio is a sequence of waveforms which have peaks, troughs, 0, just like below. How to define the x axis (y = 0) in the picture, how to choose the 0 point in the waveform since there are so many ...
3
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3answers
469 views

disadvantages of FFT, it can not extract enough frequencies without enough samples

Let's say sampling rate is $Fs = 44\mathtt{kHz}$, now I have $N = 2048$ samples, then I can get $N/2 + 1 = 1025$ frequencies. I'm confused by Matlab's FFT documentation that says the frequencies are ...
0
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1answer
32 views

Correct way to implement Discrete and Stationary Wavelet Transform?

Can someone please confirm if this is indeed the correct way to compute DWT: ...
0
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5answers
122 views

How to detect impulse like peaks - Matlab

I have a signal which is a matched filter output. whose values are given here: Amplitude values Input to this matched filter is radar return signals mixed with additive gaussian random noise. ...
0
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1answer
87 views

Frequency response of a filter - fft vs. freqz

I have designed my filter using firhalfband(N,Fo,A), which gives me the filter coefficients. Then I try to see the frequency response of it. I use these two ...
0
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0answers
22 views

algorithm Matlab function 'stream2' and 'stream3' use to compute streamline

Can anyone explain how the MATLAB functions: stream2(x,y,z,u,v,startx,starty) and stream3(x,y,z,u,v,startx,starty) compute stream lines from vector data u and v? In the stream2.m file, it calls the ...
0
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0answers
25 views

Clustering of overlapping windows (K Means)

I'm attempting the clustering of some of my data using a K-means Euclidean square method. I've broken the data down into small windows, 200 samples in size, but with a 50% overlap. I've chosen to use ...
1
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1answer
77 views

FFT Matlab - Meaning of Frequency Vector

I'm following a tutorial about the FFT. It's well explained but I don't understand the meaning of the frequency vector: ...
0
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1answer
42 views

Approximate a system frequency response with a filter in Matlab

suppose I know the frequency response of a (linear) model approximating a real physical system but only at a specific frequency $f_0$ (so basically I have a complex number whose module is the ...
1
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1answer
57 views

Make a movie from multiple images in MATLAB [closed]

I have 10 images in the folder say "D:\images\" named as frame1,frame2,...,frame10. I want to make a movie from the color images with frame rate as per choice.Also i want to save created video file in ...