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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Fitting for piecewise function, with constraints on first/second derivative

I have the following problem. We have a set of discrete points ($x_i$,$y_i$), defined for $0 \leq x_i \leq r$, where $r$ is an arbitrary value. For values of $0 \leq x \leq r$, the y value is obtained from polynomial interpolation over 6 points,…
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concept of trilinear interpolation.

I have a big confusing about trilinear interpolation. first, Interpolation's concept is estimating between two points(I'll call it as start point and end point), right? and this is depiction of trilinear interpolation from wikipedia. It has 8…
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I need to find the name of this interpolation method.

I have found a really interesting solution for interpolating cosh. First, the solver chooses the number of nodes, then, calculates Chebyshev polynomial roots on the desired interval, then finds the approximation using Lagrange construction of the…
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Interpolation of Gaussian function - minimize relative error

I have been trying to interpolate the function $e^{-x^2}$ on interval [-15,15] using standard methods like Lagrange or Newton interpolation for over a month. The goal is for it to be bound by $-\epsilon$ and $\epsilon$. No result reached. So I…
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Lagrange interpolation of a polynomial

Let $f:\mathbb{R}\rightarrow\mathbb{R}$ has such property that for every distinct $x_0,x_1,...,x_n\in\mathbb{R}$ Lagrange interpolating polynomial for $f$ in these points has degree at most $n-1$. Prove that $f$ is a polynomial. Completely don't…
xan
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Lagrange interpolating polynomials question?

We have the function : $f(x)=\cos(x) + \sin(x)$ and $x_0=0$, $x_1=0.25$ , $x_2=0.5$, $x_3=1$ a)Find Lagrange polynomial for this function. So $L_3(x)=f_0(x) l_0(x)+f_1(x) l_1(x)+f_2(x) l_2(x)+f_3(x) l_3(x)$ $f_0=\sin0+\cos0=1$,…
fdxsd
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Error term for a cubic interpolation

I have a question on one interpolation problem. The problem is below. For the given points, $x_0 = -1, x_1 = 0, x_2 = 3$ and $x_3 = 4,$ find the error term $e_3(\bar{x}) = f(\bar{x}) - p_3(\bar{x})$ for cubic interpolation of $f(x)=x^5 -5x^4.$ Give…
eChung00
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What is linear interpolation?

I am learning about linear interpolation however, we were not taught how to formally solve a problem using linear interpolation. A practice problem involving is the following: Find how long it will take for a certain sum of money to double itself at…
Kyla
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What algorithm might Google Sheets use for a "smooth line chart"? (Not the trend line)

It's not a cubic spline as the line always passes through the data points. It's not a polynomial - I have mapped a 6th order polynomial over seven data points and it is very different. Bard admits to not knowing:"The moving average algorithm that…
BlastWave
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Cubic near-minimax approximation

Most functions do not have $[-1,1]$ as the interval on which they are to be approximated. suppose $g(t)$ is to be evaluated for $a
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How to find a surface from two lines?

sorry if this is a basic problem but I don't know where to start looking. Imagine two perpendicular lines ("profiles") in a "$T$" spatial arrangement. The lines are arbitrary (empirical functions should I say?) in the sense that they don't follow…
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When should natural spline be used over not-a-knot

Given the functions $f_1(x)=\sin(2\pi x), f_2(x)=\cos(2\pi x)$ i have to interpolate them with the bounds $a=0,b=1$ over a bunch (not important) points and calculate the max error. The exercise shows that for $f_1$ the natural spline is more…
giggiox
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How to perform Lagrange interpolation on a 3D mesh?

We have a function-like system that produces a output $z$ value for each 2-dimensional $(x,y)$ input. Suppose we have sampled the system using a set of non-uniform $x,y$ inputs (inputs are not in rectangular grids), and then the generated $(x,y) =>…
user494675
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Minimum error linear interpolation of arbitrary curve using fixed number of points

Problem A finite curve, $r$, defined by $y = f(x)$, is defined by the linear interpolation between the 2 closest points (immediately higher and immediately lower) of a set points $\{(x_0,y_0), (x_1,y_1),...,(x_{N-1},y_{N-1})\}$, where the X…
Asensio
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Smoothing arbitrary curve changes

I'm a programmer, my math knowledges are very limited, so if my post is misplaced - just let me know There is an arbitrary curve with regular step. The value at specific point should be changed to a specified new one. I need to adapt/interpolate…
TheIgors
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