Questions tagged [interpolation]

Questions on interpolation, the estimation of the value of a function from given input, based on the values of the function at known points. It is necessary because in science and engineering we often need to deal with discrete experimental data.

Interpolation is a useful mathematical and statistical tool used to estimate values between two points on a line or curve.

What Is Interpolation?

Interpolation is the process of deriving a simple function from a set of discrete data points so that the function passes through all the given data points (i.e. reproduces the data points exactly) and can be used to estimate data points in-between the given ones.

To help us remember what it means, we should think of the first part of the word, 'inter,' as meaning 'enter,' which reminds us to look 'inside' the data we originally had.

Applications: This tool, interpolation, is not only useful in statistics, but is also useful in science, business or any time there is a need to predict values that fall within two existing data points. It is also used to simplify complicated functions by sampling data points and interpolating them using a simpler function. In the mathematical field of numerical analysis, interpolation is a method of constructing new data points within the range of a discrete set of known data points. In engineering and science, one often has a number of data points, obtained by sampling or experimentation, which represent the values of a function for a limited number of values of the independent variable. It is often required to interpolate, i.e., estimate the value of that function for an intermediate value of the independent variable.

The details, techniques, and precise meaning of interpolation depend heavily on the sub-discipline of mathematics, therefore you are encouraged to use additional subject tags such as , , , or when appropriate.

1995 questions
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3D Interpolation for Irregular Grid

I have a cloud of data points in three dimensions (x,y,z) that carry a value of some sort (lets say temperature T). I was wondering what the best options were for interpolating the temperature to a new point within the cloud of points. The points I…
Travis
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4 point quadratic curve

I can define a curve that passes through 3 points using a quadratic equation: ax2 + bx + c = 0 I would like to know is it possible to define a curve that passes through 4 points using: ax3 + bx2 + cx + d = 0 Cheers
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How to calculate the amount of time spent interpolating from one tempo value to another

I am writing a music creation program where the user is allowed to change the tempo throughout the track. If the user had a set tempo or only changed the tempo at discrete intervals I could easily calculate the time by taking the tempo, and the…
shnudm
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Inverse distance weighting where neighbouring values are zero

I am trying to interpolate a set of rainfall data in order to find the rainfall at an unknown point. I have been using the inverse distance weighting interpolation method (details given here: http://en.wikipedia.org/wiki/Inverse_distance_weighting),…
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Writing a Hermite Interpolation script

Tasked with writing a MATLAB script that computes the Hermite interpolation of a function. Specifically, it asks to find: $$p(x)\in \Pi_{2n+1} \text{, such that } p(x_0)=f(x_0), p'(x_0)=f(x_0)... ,p(x_n)=f(x_n),p'(x_n)=f'(x_n)$$ Can anyone explain…
Neurax
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Two sets of number ranges where one influences the other, how to find the intersection point?

Suppose I have the following number ranges: a = [x = 1, y = 5] b = [x = 9, y = 3] Now say a donkey is travelling between the number range 'a' and a horse is moving between number ranges 'b'. The amount the horse has moved is directly proportional to…
meds
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how to show a data set satisfying a equation?

I have a set of data points like $(1,6)$, $(4,9)$, etc., and I am given a specific linear equation with two variable like $y = a/b + b x$. How can I show that the data points fit the curve?
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how to interpolate a 2d function with 6 points?

I'm implementing an algorithm that uses a so called 6-point interpolation, which I never heard before. In the article I'm reading it's described like this: $\phi(p\Delta x, q\Delta y)=[q(q-1)/2] \phi_{0,-1}+[p(p-1)/2]\phi…
Diego
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cubic function of the two points (2,0) (4,0)

How can I find the cubic function of two points. I have the $y$-intersect $(0,2)$ and the $y=0$ intersect with the x-axis $(4,0)$. The equation should have the form $y=x^3+2$. But when I try to calculate the intersect with the $x$ axis by using the…
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Piecewise linear interpolation

A really simple question - how does it work? Linear interpolation is quite easy and understandable: for (i = 0; i < N; i++) { X = ((A * i) + (B * (N - i))) / N; } But how does it work with more than two point? I want to make it as smooth as…
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Lagrange Interpolation -- Challenge Problem

Say you're performing Lagrange Interpolation on a function $P(x)$ and you've found that $$ P(x) = \sum_{i = 1}^{11} \Delta_i(x) $$ given the eleven points $(1, P(1)), (2, P(2)), ..., (11, P(11))$. Remember that $$ \Delta_i(x) = \frac{\prod_{i \neq…
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Interpolant from Dopri5 schema

Im trying to understand the linked paper (cf paper), please correct me if my understanding is wrong ! Im looking to get an interpolation function from the result of a Dormand Prince (RK45) integration step, first introduced in the paper. In order to…
thmo
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Trouble Understanding Tetrahedral Interpolation

(This is more specifically referring to 3D LUT creations, incase there are other uses of tetrahedral interpolation, which I'm sure there are) I've been reading about spline interpolation which visually has always been relatively intuitive to me, in…
vannira
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Mapping Decreasing Volumes to Increasing Pixels in a Chart Application using Linear Interpolation

As a developer building a chart application, I'm using linear interpolation to map time values to pixel positions on the screen. My current approach utilizes the following function: fun interpolatePixelByTimestamps( startPixel: Double, …
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Discrete to Continuous Sinc Filter.

I'd like to know, how to implement a curve interpolator using only past and current data samples. The goal is to get a smooth curve out of discrete samples that're fed in real-time. To this end, I discovered the Sinc interpolation and filter, and I…
DannyNiu
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