Signal Processing Stack Exchange
Signal Processing Stack Exchange

Questions tagged [interpolation]

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

Usually, it is required to interpolate (i.e. estimate) the value of that function for an intermediate value of the independent variable. This may be achieved by curve fitting or regression analysis.

Source: Wikipedia.

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When is cubic spline interpolation better than an interpolating polynomial?

The following plot is a slight variation of an example in a text book. The author used this example to illustrate that an interpolating polynomial over equally spaced samples has large oscillations near the ends of the interpolating interval. Of…
Ted Ersek
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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 lecture notes, slides and Youtube videos that…
goocreations
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Artifact in Bicubic interpolation

I wrote an algorithm to do bicubic interpolation of an image. I used the method desribed in the wikipedia page. On simple images, the result looks good, but on more complex ones, I got strange artifacts in non-smooth zones. What could be a probable…
gwenzek
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Sequence expansion by zeros and interpolation - does it insert additional frequencies?

I am struggling with understanding the consequences of oversampling on the frequency spectrum of the signal. If I understand correctly, with an oversampling rate of 8X we insert 7 new values for each value measured. In case we keep this new values…
user7216373
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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 point out even the most basic errors. I have tried…
DohnJoe
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How to subsample shift with sinc interpolation?

Does anybody know of a way to shift data by a fraction of a sample by using sinc interpolation? For example, shift an image to the right by 0.1 pixels. I'm struggling to find a formula or reference that explains how to generate such a kernel, and I…
Mikhail
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B-Spline for computing image warps

I have 2 images A and B, and a set of point correspondences S which indicate the position of the same point in the 2 images. The goal is to fit a grid on the image A and warp the grid such that the points get close to the points in image B. This…
Paul92
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How should I interpolate on a triangle mesh?

I have a triangular mesh (generated from a Lidar point cloud). On this mesh I do point measurements using two instruments. One records M amplitudes of frequencies in the visible range and the other records N amplitudes of frequencies in the infrared…
Andy
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Multi-stage interpolation

So I've read here Multi-Stage digital FIR filter vs Single stage FIR filter. Which is better? if you want to interpolate by a great number, it's always better to do so in multi-stage interpolations so it won't be as costly as a single interpolation.…
researcher9
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Sinc interpolation of pure sine wave sampled just at Nyquist frequency

Following this question: Shannon-Nyquist theorem reconstruct 1Hz sine wave from 2 samples could you explain the algorithm to apply for sinc interpolation to avoid the "sawtooth" effect due to linear interpolation? (It seems to me that the…
SheppLogan
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Interpolating irregularly missing data points of regularly spaced data

If I have a set of regularly spaced sample data (spacing $\delta x$) and some of my data is missing (zero) but not at regular intervals, i.e. $[a_0, (missing), (missing), (missing), a_4, a_5, (missing), a_7, a_8, a_9, a_{10}, ...]$ Can digital…
keith
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Variable sample rate interpolation

I have a set of data over which I would like to interpolate, with a sampling rate say about $f_0$ Hz with a significant uniform random sampling jitter, such that it's more or less: $$f_0 - \frac{1}{4}f_0 \le f_s \le f_0 + \frac{1}{4}f_0.$$ Normally,…
Bugasu
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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. I create functions that calculate A and B…
Mr Jedi
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interpolation: why I can see the original sequence in the interpolated data only when (N/M) = integer

I am trying to understand the zero-padding in frequency domain and discovered that original sequence in interpolated data only when (N/M) = integer where N and M are the lengths of output and input. clear all; close all; M = 9; N = 18; m_p = (M…
jomegaA
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What is the right way to interpolate a 2D grid?

Let's say I have a 2D grid of temperature measurements in some area and I want to estimate the temperature at some point between the samples. Or at every point, which would basically amount to upscaling an image. Which interpolation method would…
fhucho
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