Interpolation is a method of constructing new data points within the range of a discrete set of known data points.

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Savitzky-Golay filter parameters

I am trying to smooth a series of data in order to obtain a continuous function that could represent that given data set. It came out that the Savitzky-Golay method could be a good way. Now, I don't ...
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Interpolating on the borders of differently-resolved images

I'm creating a three-dimensional model of the earth based on SRTM height data. The data set is pretty huge, so only a small fraction of the data is available at any given time. The height data is ...
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Trying to understand downsampling and then upsampling

I am trying to understand how this works, specifically, what the DTFT of each step looks like in each step of the chain (for understanding). I am not looking for an answer like because the input ...
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60 views

filter and resample or resample and smooth?

Currently doing some signal analysis in python for a major project in my physics degree which is due really soon. I need some help! Say I have two signals, f(t) and g(t) which are recorded over the ...
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71 views

Upsampling signal for cross correlation

I am recording a 17khz signal at a sample freq of 44.1khz. I want to perform cross-correlation between the received and transmitted signals for calculating TDOA. But when I do xcorr, the results are ...
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How do you interpolate between points in an image (2D), e.g. using splines?

I can understand just fine how to use 1-dimensional interpolation on data points where one coordinate is a function of the other: y = f(x). However, when we have an ...
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Extend linear spline interpolation to cubic spline interpolation - how calculate derivative

I'm trying implement in Java cubic spline interpolation based on this document: http://www.geos.ed.ac.uk/~yliu23/docs/lect_spline.pdf At first they show how to do linear spline and it's pretty easy. ...
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Questions regarding the Yin algorithm

I decided to implement the Yin algorithm for pitch estimation in monophonic music as a school project. I have studied the paper, but I don't understand some parts of it: In Step 3 - Cumulative mean ...
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24 views

Intepolation frequency repetition after $f_s$ or frequency folding at $f_s$

What I read is signal repeats at interval of $f_s$. The fold image comes after $f_s/2$ not $f_s$ so why a fold shown in diagram? In the diagram attached, at $f_s$ the folded image of signal is shown ...
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265 views

Why is biquadratic interpolation for image resampling rarely done?

Related question: What are the practically relevant differences between various image resampling methods? Bilinear and bicubic interpolation for image resampling seem to be fairly common, but ...
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229 views

Higher order spline interpolation

I noticed that spline interpolation with a degree higher than 3 (everything beyond cubic splines) have a very high interpolation error, hence the prediction is mostly awful. I've come across various ...
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interpolation of filter coefficients

i've read that it is possible to interpolate between two sets of filter coefficients (if they are close of course), but how to interpolate between two sets of coefficients which are of different ...
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48 views

Upsampling Methods for Computed-Tomography

I have two sets of data of given Field of view, one of them only covers a subset of the FOV of the other. I therefore want to upsample the one with the larger FOV to combine it with the other one. So ...
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304 views

polyphase sample rate conversion with non-integer factor

I want to do sample rate conversion by subsequently upsampling with factor I=5, and then downsampling with factor D=9. I have designed a nyquist sample rate conversion filter h() of length M, with ...
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138 views

convolution based image interpolation

From a book, I learned that image interpolation (or upsampling) can be written as a convolution like this: $$g(i,j) = \sum_{(x,y)}f(x,y)h(i-rx,j-ry)$$ while $r$ is the upsampling rate. But I have a ...
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157 views

What are the effects on filtering upsampled data without interpolation?

I have an application that displays several signals from different sensors at various sample rates. In order to display the data, I "stretch" the signal by repeating samples to match the highest ...
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596 views

Is interpolation (interp1) better than FIR filtering when rational integers are close to 1?

Question I've been attempting to resample a GPS signal in MATLAB. I've built a few FIR filters using fvatool and from handmade transfer functions (punched out with ...
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65 views

Is there a need of Point interpolation before proceeding for gaussian smoothing of an incomplete distribution?

Suppose there is a distribution that has values sampled on the interval 1-25 with corresponding sample values that have to be smoothed. For example: ...
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307 views

Interpolated FIR filter

I am confused about this Q&A : Interpolation by factor of 2 If my input signal $$ x[n]= x0,x1,x2,x3 $$ then according to the threads explaination my $v[n]$ will be $$ v[n]=x0,0,x1,0,x2,0,x3,0 ...
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305 views

Interpolation by factor of 2

I want to up-sample my input signal by a factor of 2. I saw zero padding followed by Low Pass Filter method being used in few cases. But still i need some help in this. Say i have 10 input samples and ...
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166 views

Interpolation vs Interpolation Filter?

Hi guys, I've been reading some papers on - how to remove ghosting artefacts from the Fourier Slice theorem applied to a 3D discrete image volume. The papers mention that in order to remove ghosting ...
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147 views

Calculate interbeat intervals

I'm currently reading a paper and I can't seem to make sense of a certain part. A link to the paper: removed The part I don't quite get is on page 286 (after the part where they explain their ...
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358 views

Interpolation in Contrast Limited Adaptive Histogram Equalization

I have been trying to implement the CLAHE algorithm and came across this page which states step by step procedure for the algorithm. I understand the initial steps to perform HE of tiles in the ...
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304 views

Fitting piecewise splines to noisy data

I have a system that gives me a noisy data set similar to the one generated by this matlab/octave code. The y-axis represents the signal intensity and the x-axis represents spatial distance. ...
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654 views

How does subpixel image shifting using DFT really work?

I am trying to assess the quality of several image interpolation methods for an application that involves generating subpixel-shifted images. I thought I could compare the results of a subpixel shift ...
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302 views

creating a seamless signal / loop using interpolation

I'm trying to create a seamless loop using a "non-periodic" signal using interpolation to smooth out the beginning and the end but I'm still getting a click at the beginning when it loops and I listen ...
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170 views

How to mix two signals without changing the overall loudness?

I have two audio signals that I want to mix at various mixing ratios. Initially, I simply went for something like $y(t) = \alpha \cdot x_1(t) + (1-\alpha) \cdot x_2(t)$ where $\alpha$ is the ratio ...
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Interpolation with an FIR filter

How can I use interpolation with an FIR filter? I am more familiar with interpolation such as nearest distance interpolation, linear interpolation and so on. Suppose a signal is given as the ...
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2k views

How can I resample a signal with an arbitrary factor (e.g. 128000Hz to 16000.1Hz) in Matlab?

I need to simulate the sampling of a continuous (fsCtu = 128000Hz), acoustic signal with two microphones that have a slight offset in sampling rate (fsMic1 = 16000, fsMic2 = 16000.1) in Matlab. What ...
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309 views

Real-valued ringing when zero-padding odd-length FFT

So I'm trying to write a frequency-domain interpolator that zero-pads the frequency response of a signal and inverse transforms. There's two cases I have to deal with: Even-length response - have ...
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1k views

Time domain interpolation using FFT with zero padding on the end

I've got a situation where I'd like to use an FFT to do interpolation in time on some complex data (I need to go to the frequency domain anyways to window my data). The notional way of doing this ...
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426 views

How can I smoothly interpolate between 2 position?

I've got a 1D signal (position of a servo motor over time) and I've extracted 'peaks'/'key' positions picking running average "local extrema" points. Below is are 2 plots from 2 servos and the white ...
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232 views

How to prevent “zipping” effect on a modulated fractional audio delay line? (Flanger)

I am implementing a Flanger using a fractional delay line. I am modulating the length of the delay line using a sin function. The delay line already uses linear interpolation to compute the delay ...
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How do I numerically calculate a function from its noisy gradient?

I have the model $\ s(x,y)=x^2+y^2, 0 \leq x \leq 1, 0 \leq y \leq 1 $. Instead of observing the model directly I am observing the derivatives of the model + some noise (e): $\ p(x,y)=s_x+e, ...
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255 views

Plotting DNA chromatogram trace data

Sanger DNA sequencing produces a chromatogram trace which can be visualized with a number of programs, including FinchTV or ChromasLite. The raw data consists of co-ordinates for each of the four DNA ...
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Interpolation of a gray scale image in matlab [closed]

I want to fill the black areas with the value of neighboring pixels. Kind of interpolation. Can any one suggest me how Can I do in matlab.
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FFT, interpolation and phases

I am trying to understand how to interpolate discrete sinusoidal data that I (for now) generate myself, and I get problems that I don't understand. I'm a newbie in this field so do not hesitate to ...
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475 views

Sense of zeropadding in a time domain

I have the task related to Radon transform which contains a subtask which uses resampling by means of DFT. Let's consider the non-periodical discretized signal (Fig.1) (for example the string of ...
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326 views

How can I automatically classify peaks of signals measured at different positions?

I have microphones measuring sound over time at many different positions in space. The sounds being recorded all originate from the same position in space but due to the different paths from the ...
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925 views

Differences between filtering and polynomial regression smoothing?

What are the differences between classical low-pass filtering (with an IIR or FIR), and "smoothing" by localized Nth degree polynomial regression and/or interpolation (in the case of upsampling), ...
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801 views

How do I use a Savitzky Golay filter to find local maxima (in between samples) in a discretely sampled 1D signal?

I have a seismic signal y(i): Here I have found one maximum: i=152.54, y=222.29 manually and plotted it in red. I want to find all maxima automatically. I read that the Savitzky Golay Filter (SGF) ...
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707 views

Finding local peaks in-between samples

I have n discrete samples of a seismic signal y[n]: I want to find local maxima in the signal. A naive test for if y[n] is a maximum would be: y[n]: maxima if y[n] > y[n-1] and y[n] > y[n+1]. ...
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235 views

What interpolation methods can I use to get the tightest fit for these curves?

I am working with MRI images of the brain that have certain areas marked by hand like and . I am trying to come up with an interpolating function that will let me describe such curves so that I can ...
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Frequency-domain zero padding - special treatment of X[N/2]

Suppose we wish to interpolate a periodic signal with an even number of samples (e.g. N=8) by zero-padding in the frequency domain. Let the DFT X=[A,B,C,D,E,F,G,H] ...
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726 views

Calculating the PDF of a waveform from its samples

A while ago I was trying different ways to draw digital waveforms, and one of the things I tried was, instead of the standard silhouette of the amplitude envelope, to display it more like an ...
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How can I design Nyquist interpolation filters with the Parks-McClellan algorithm?

We can easily design interpolation filters that obey certain frequency-domain constraints using the Parks-McClellan algorithm. However, it's not immediately clear how to enforce time-domain ...