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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How many points can be fit by a single sine function?

Consider a sine function parameterized by amplitude, frequency, phase, and constant offset. In other words, $h(x) = a\sin(fx + p) + c\tag*{}$ where $a$, $f$, $p$, and $o$ are arbitrary real numbers. Suppose we are also given a set of points…
Ted Hopp
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How to interpolate points between 2 points

I have 2 points X,Y (for example [5,10] and [20,30]) and I need to interpolate points between these 2 points in order that all this points are spaced by 1 measurement unit. Let's pretend I am using cm (as my measurement unit) and I have a point at…
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Linear interpolation with two points

Question: $p(x)$ is the linear function that interpolates $\sin(x)$ at $0$ and $\frac{\pi}{2}$. And I need to show that $\ |p(x) - \sin(x)|\le\ \frac{1}{2}(\frac{\pi}{4})^2$ My attempt: $\ |f(x)-p(x)| \le (K_n/(n+1)!) * |W(x)|$ where $\ K_2 =…
wrenyoong
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Extending cubic splines interpolation into n input variables. Is it possible?

I have the equation for cubic spline interpolation, and I can see how it works for a data set in the 2d Cartesian coordinates. I was wondering if there is a general form to the equation that allows for interpolation for n input variables. For…
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Lagrange interpolation, syntax help

I am told, the basic interpolation problem can be formulated as: Given a set of nodes, $ \{x_i, i=0, ..., n\} $ and corresponding data values$\{y_i, i=0, ..., n\}$, find the polynomial $p(x)$ of degree less or equal to $n$ such that…
user120625
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conditioning of the monomial basis

It is well-known that the Vandermonde matrix is ill-conditioned when all nodes, i.e., the points that generate it, are real. I have read the following on a paper: The ill- conditioning of the Vandermonde basis has an elementary explanation in cases…
Leibniz
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Convex curve interpolation

I have a set of points $(x_0,y_0)$ ... $(x_N,y_N)$ with the $x_i$ increasing and the $y_i$ such that $\frac{y_{i+1} - y_{i}}{x_{i+1} - x_{i}} > \frac{y_{i} - y_{i-1}}{x_{i} - x_{i-1}}$ Is there a well-known interpolation scheme that would give me a…
d--b
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Interpolation problem: scattered points => "full grid"

I have 2D matrix of size like 512x512 or so. I also have a set of points with coordinates within bounds of the mentioned matrix ([0..512,0..512] in this case then) and each such point stores a property value (e.g.temperature). The points usually lie…
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variogramas kriging

In order to find the altitude of a surface, we use the following method. My question is: What is the name of this method? We have $$ A=\begin{pmatrix} a_{1,1} & .. & .. & a_{1,n}&1&x_{1}&y_{1}\\ .. & .. & .. & ..&1&x_{2}&y_{2}\\ .. & .. &.. &..…
Bek
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interpolation inequality meaning

Good evening, I'm so sorry if my question is ridiculous a little bit but it is important for me; 1- I would like to understand what we mean by an interpolation inequality? 2- What are the condition must be satisfied by an inequality to give it the…
A s
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Spline interpolation on a growing series of data

In a project on which I am working, I have a computationally expensive process to calculate a value for a given point in time. As I am working with RF data at approximately 16MHz, this would be impractical to calculate for each and every…
Darran
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Interpolation of 3 points

I want to interpolate a function given 3 $x$ points ($0$, $0.5$ and $1$) and their correspondent $y$ values. $x$ values will be always between $0$ and $1$. How can I interpolate a given value, like $0.3$? And what about if I add more sample data,…
Javier Marín
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how to make 2d shape deformations?

I'm trying to make an animation transition between 2 shapes, example: transform a square into a circle... or transform a triangle into 2 squares pretty much like this: https://i.stack.imgur.com/hSxul.jpg (no rep for posting images) my first idea is…
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Average value within four points

Say you have four points at the corners of a unit square, and each point has a value associated with it (we can use numbers here, but the solution needs to work for any continuously interpolatable value, such as RGB colors in linear space). Assuming…
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Understanding divided difference table

To Construct a divided-difference table using the given value for x and f(x), This solution table seems so confusing to me i understood how the value of f1[] was calulated (-1-(-7))/(1-(-1)) = 3 and the same way for others. But using the same rule…
rakibtg
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