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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point on this line doesn't make sense

This is trivial by I'm stumped. I am trying to find the $x$-coordinate of a point on a line so that I can generate parallel diagonal lines on a graph- see image. My slope is $m=-1$ and one point $(x_1,y_1)$ is $(1000,0)$. I would like to find the…
val
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How can I find the base price and price per unit?

I have a table filled with retail prices for various width*height combinations. How can I approach to find the formula for this chart?
S.A
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What are the pros and cons of Newton's Interpolation formula?

What are the pros and cons of Newton's Interpolation formula for unequal intervals against Lagrange's interpolation formula?
user366312
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How to find the equation from data?

I know things about linear/quadratic fittings etc. I'm just wondering, if i know a set of data for value e.g. z=[-2.563 -0.1932 -0.1502 -0.1102 -0.836 -0.5234] and l=[1 2 3 4 5 6] m=[6 5 4 3 2 1] I want to write out a function of z in terms of l and…
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How to find 3D coordinate of a 2D point based on a set of 3D points (possibly non-coplanar)?

I have a set of 3D points (I'll call them "outer" points) and a 2D point ("inner" point). I need to quickly calculate a "good" third coordinate for the inner point so that it would place the constructed 3D point as "close" to the outer points as…
lexicore
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How to determine the function factors in order to fit the curve?

I am trying to calculate innovation and imitation factor by ovserving the usage of specific service among the population. After going through an overview of the paper I wrote the fuction in matlab: function F = Bass(x, inputData) m =…
niko
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lerp with time parameter?

I'm implementing lerp function with time parameter and got stucked at how to involve time(t) in the formular. I have the original coordinates of vP(xP,yP) and the destination coordinates of vM(xM,yM). And it was asked to go through the distance at…
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Create function from a list translated geo coordinates to points

I'm a software developer and I want to create a function from raw data which I collected. The data relates to a satellite image of Europe (Germany). I have a list of geo coordinates and the resulting coordinates in the image. {lng: -1, lat: 47, x:…
DonAgo
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Derivation of linear interpolation?

Anyone know a good derivation of the linear interpolation: $$\frac{y-y_0}{x-x_0}=\frac{y_1-y_0}{x_1-x_0}$$ Wikipedia gives one, which I don't understand.
mavavilj
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Why do I have the wrong ratio for this linear interpolation question

$$f(x)=5x^3-8x^2+1$$ There is a root between x=1 and x=2, use linear interpolation (using similar triangles) to find the root correct to 1 dp So I tried doing this: $$f(1)=-2$$ $$f(2)=9$$ so the ratio ought to be $$(a-1)/(2-a)=2/9$$ which you then…
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Method of Undetermined Coefficients (Vandermonde) on data points?

I know how to interpolate using Vandermonde and obtain p(x) if the data points are given as something like p(-1)=1 p(0)=0 p(1)=1 But what if derivatives, p'(x) are given as data points additionally? example data points: p(-1)=1 p'(-1)=2 p(0)=0 …
Chase
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Find root with chord method

With chord method find real root of the equation $x^3 - 2x+1-{e^x\over2} = 0$ accurate to $0.001$ I can not perform first condition in the method of chords
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Numerically find the intersection point between two sets of data.

I'm looking for an efficient way to determine if two paths (sets of x,y coordinates) intersect at a point. Input - (x,y) from a Mercator Projection (longitude,latitude) coordinates Output - Intersection point I looked at this question here: Solve…
bren
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Polynomial interpolation of $n+1$ points but ensure last coefficient is a certain number?

I have $n+1$ data points $(x,y)$, and I want to create an interpolating polynomial as described here https://en.wikipedia.org/wiki/Polynomial_interpolation. However there is a twist, I want to ensure $a_0$ is some real rational number. Basically…
omega
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$\bar x$ value for $f(\bar x) = 4.5$ with tabled values

The exercise asks for the $\bar x$ value as $f(\bar x) = 4.5$ using linear interpolation. I couldn't reproduce a table with MathJax, so I'll put the tabled with data as: $f(2) = 10$ $f(4) = 13$ $f(5) = 6$ $f(7) = 5$ $f(9) = 2$ Since I have $f(\bar…
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