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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Why do we need to set the remainder expression like this?

I need to find interpolation polynomials and their remainder expressions satisfying the conditions $P\left(x_{i}\right)=f\left(x_{i}\right)(i=0,1,2) $ and $P^{\prime}\left(x_{1}\right)=f^{\prime}\left(x_{1}\right)$. I wonder why I need to set the…
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Finding the coefficients of a polynomial

There is a polynomial $f(x,y) = \sin(\theta) x^2 + \cos(\theta)y^3 + x^2+ x^3y^2 +5$, where $\theta= g(x,y)$. Can we find the coefficients of $f(x,y)$ using any interpolation method?
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Product of polynomials with restrictions for values at three points and all coefficients (but the absolute one) non-positive

this question is closely related to my other question from yesterday : Interpolation of three positive values at 0, 1 and 2 by a polynomial with non-negative coefficients. Let $ g $ be a univariate polynomial with real coefficients (actually…
diddy
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deceleration with fixed distance over time

Hi I'm doing a bit of mobile phone game development using a physics engine and have come across a mathematics problem thats stumped me. basically object A has a velocity vector of dx:0, d:300 object B has a velocity vector of dx:0, dy:300 object A…
hoboBob
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Interpolation of irradiation data in comparison with commercial program

Hi there and thanks for reading this question, I'm having problems interpolating quarter hour values for irradiation data. The given hourly data looks like this: h W/m² [09] 0 [10] 4 [11] 15 [12] 56 [13] 77 [14] 37 [15] 0 This is not…
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linear interpolation $f(x)$ given $f(1)=1$ $f(5)=2$ and $f(7)=5$?

linear interpolation if $f(1)=1 $, $f(5)=2$, $f(7)=5$. What is $f(x)$? I have tried with Lagrange but it doesn't work or maybe I am doing it wrong
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Interpolation of a polynomial given values at certain points and (higher) derivatives at those points. (Generalized Lagrange Interpolation)

Suppose we where given the following values of $P(x)$ : $P(1) = 2, P'(1) = 3, P(2) = 1, P'(2) = -1, \text{ and } P''(2) = 1.$ How can we find a polynomial of degree less than 5 that satisfies these conditions using generalized Lagrange…
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Interpolation question and negative results

I have spreadsheet . I did interpolation on it. Negative values showed up I used this YouTube video: https://youtu.be/Wc4WeYN7MT0 Data is not time indexed. Question: How do I interpret negative values, if results should be positive?
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Difference between interpolation method - give me some function

What are some functions that gives vastly different results when interpolated with spline, in comparison to linear or to polynomial interpolation? For example i tried with sigmoid and bump function, both gives almost same results, no matter which…
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Parabolic Interpolation

I'm reading this lecture page: http://fourier.eng.hmc.edu/e176/lectures/NM/node25.html and towards the end of the discussion, it says that upon finding $x_{min}$, the process can be repeated using a new set of points by eliminating one of the old…
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How to find the equation of the curve using the set of points?

I have the following data available. 1572415440 1.110919 1572415500 1.110919 1572415560 1.110915 1572415620 1.110908 1572415680 1.110892 It forms a curve which is somewhat concave. You can see that…
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How to interpolate the inverse square law?

I am a relative novice in terms of mathematics, but I am trying to understand how to approach a problem I have. I have an area light source that is 0.5 m² that produces 3500 luminous flux. As I understand it, light has a falloff that follows the…
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Understanding Lagrange error.

Here is an example from my Numerical Analysis book (Burden & Faires). Trying to understand Lagrange error, but I do not understand the statements in bold. In example 2 we found the second Lagrange polynomial for $f(x)=x^{-1}$ on [2,4] using the…
user52272
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How to create an equation from linear interpolants

I found this Wikipedia article on Linear Interpolation. The third figure down depicts a data set 0 0 1 0.8415 2 0.9093 3 0.1411 4 -0.7568 5 -0.9589 6 -0.2794 which I got from checking out the Gnuplot source. In the article it talks about this…
147pm
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How to do interpolation using the newton basis?

I have these data points. $f_i(x)= \{10, 11, 14\}$ $x_i= \{0, 1, 3\}$ then the basis functions are. $\pi_0 = 1 \\\pi_1=(x-x_0)=x \\\pi_2=(x-x_0)(x-x_1) =x(x-1)$ So the matrix will become. $\begin{bmatrix} 1 & & & 10\\ 1& 1 & & 11\\ 1& 3 & 6 &…