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.

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Polynomial interpolation vs polynomial curve fitting

If we have $n + 1$ points $(x_i,y_i$), then we can use interpolation methods (Lagrange, ...etc) to find a polynomial of degree $n$: $$P_n(x) = a_0 + a_1x + a_2x^2 + \cdots a_nx^n$$ In curve fitting, we search for a polynomial that best fits the…
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Shepard interpolation algorithm

Classic way to get a value based on other points in Shepard (Inverse distance weighting) method: $$F(x,y) = \Sigma_{k=1}^{N}w_{k}(x,y)f_{k} / \Sigma_{k=1}^{N}w_{k}(x,y) $$ where $w$ can be compute as some expression with metric (euclidian for…
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Rescaling and linear interpolation

Is rescaling as explained in this question and linear interpolation two names for the same thing or are there any differences between them?
user346461
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Bilinear interpolation example

I just do not understand what we are supposed to do when we want to scale a matrix with using the method of bilinear interpolation. Let's say we hjave a 3x3 matrix as written below. \begin{bmatrix}1&1&1\\1&2&2\\1&2&3&\end{bmatrix} Can you please one…
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Interpolate values in 2D space + time (3D interpolation) of multiple objects in concert

With a given dataset, I have multiple objects that move, in concert, inside a 2D eucledian space. The dataset of one object is given like this: frame x y 0 10 22 1 NaN NaN 2 26 14 ... 8999 54 45 9000 59 43 To keep the system…
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Efficient Integer Interpolation

Let $n\in\mathbb N$. Let $\{{x_i\}}_{i=1}^{n}$ be $n$ positive real numbers. Can one think of a fast way to construct a function $f$ such that $f(x_i)=i$? (i.e. $f$ maps $\{{x_i\}}_{i=1}^{n}$ to ${1,2,3,...,n}$. At least a way faster than Lagrange,…
Troy McClure
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How to determine if a period of missing values is short or long

I am dealing with a dataset that has some missing values. I read an article where it is stated that some imputation methods may work better in short periods of missing values, while others may provide better results when applied to long periods of…
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Mapping min and max value to 0.1 and 1 and found equivalent number between

I'm trying to find a solution for this problem, I have a min and a max value that i want always map as min 0.1 and max 1, so for example: i have 48 and 97, so 48 will be my 0.1 and 97 will be my 1. Now i want map a number between 0.1 and 1 in the…
Piero
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Discrete model fitting or interpolation possible satisfying only selected points

Suppose I have a discrete data set. Let the data set be points from $\mathbb{Z}_p \times \mathbb{Z}_p$ represented by $\{(\bar{x_1},\bar{y_1}),(\bar{x_2},\bar{y_2}),\cdots,(\bar{x_n},\bar{y_n})\}$ where p is a prime. Is there a way to obtain a…
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will polynomial interpolation give a polynomial satisfying those points only

when you derive an interpolating polynomial say through 3 points is there a chance for that polynomial to satisfy any other point other than those 3 points? (Any other point in the same domain)
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Is there cases where interpolation is impossible?

I just learned interpolation and have been looking through it. It seems like for every data set, interpolation is possible -- is this true? Is there any cases it is not possible to use interpolation? Any hints or help on this question will greatly…
이다은
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Interpolation polynomial of degree at most n

I came across to this type of a question and I don't know how to solve it let's say f(x) = cosx and we are given x0 = 0, x1 = 0.6 and x2 = 0.9 In the question it is asked to construct interpolation polynomials of degree at most one and at most…
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finite element interpolation formulae

Is there a place where I can found formalas used for interpolation in the Finite Element Method? I'm look for recipes, where formulas are given for basic 2D and 3D elements, that can just be applied, without any theory. In other words, there are a…
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Interpolation of trigonometric functions

I want to evaluate $f''(x)$ for $f(x)=\sin(x)$ and $x=\frac{\pi}{6}$ and then determine the error in the approximation of $f''(\frac{\pi}{6})$. From previous knowledge, I know that to find an approximation, we need to compute the first derivative…
Ben
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Interpolate f at the points $x-h , x $ and $x+h$ by a quadratic polynomial $p(x)$

Interpolate f at the points $x-h , x$ and $x+h$ by a quadratic polynomial $p(x)$. Let $ \ p(x)=a+bx+cx^{2} \ $. Now,\begin{align} p(x-h)=f(x-h)=a+b(x-h)+c(x-h)^{2}, \\p(x)=f(x)=a+bx+cx^{2} , \\ p(x+h)=f(x+h)=a+b(x+h)+c(x+h)^{2}, …
MAS
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