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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Interpolation of Symmetric Data

For symmetric data $(x_i,y_i), i=-n,-n+1,..., n-1, n$ such that $x_{-i}=-x_i$ and $y_{-i}=-y_i, i=0,1,...n$ what is the required degree for an interpolating polynomial $p$? Since there are $2n+1$ data points (one for each $\pm n$ plus one for…
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Interpolation of rounded data

I would like to interpolate (not fit) a data set whose points have been rounded. Lets say I have some observations $y_i$ of a function sampled at $x_i$. The sample locations $x_i$ may be considered exact, but the observations $y_i$ were rounded to…
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Newton 3d grade polynomial , simpson 3/8

Hello guys and sorry for my bad English , i have the following homework i should composite Newtons polynomial interpolation 3d grade , Simpsons 3/8 method with matlab ! But i have some trouble, i have the following formula and i should make the…
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Do nth degree polynomials derived using Least Squares Interpolation always have n+1 intersections with the function?

I have recently studied Interpolation Techniques in my College Numerical Methods class and I have this question: If we have a function $f(x)$ and we are asked to use Least Squares Interpolation(LSI) to derive an approximating polynomial of the nth…
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Determining whether a function is Piecewise Polynomial

I am trying to determine whether or not a function is piecewise polynomial. The function is as below: Let $\ X$ be a continuous random variable with support on $\ \Omega_x$, and with corresponding cdf $\ F$. Is the function $g_r$, $r\geq 1$,…
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Merging two univariate functions gracefully

Suppose I tell you that $$ f(0) = 0 $$ $$ f'(0) = 0 $$ and $$ f''(0) = a $$ for known $a>0$, whereas for large $x$ $$ f'(x) \approx \cosh^{-1}(x) $$ for $x>2$. Knowing nothing else about $f(x)$, what is a sensible interpolation consistent…
Quant
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Interpolating polynomial given only Y values

Can we reconstruct a polynomial with only Y values? What if the number of Y values are far more than the degree of the polynomial? Also can we obtain the root of this polynomial with this Y's value without interpolating?(i.e. without knowing the…
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How to interpolate this table

I have a 3D function(al) f whose independent variables are A,C,D and E. Various tables are provided to show the function values. For each individual table, value of A is a constant. The nth table is provided for A + nk where k is a constant. The…
Vinod
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Interpolate daily values from monthly averages

I have a list of monthly production guarantees and I want to estimate daily values. Dividing monthly totals by days/month works, but when graphed, leads to a chunky piece-wise plot. I could use a spline interpolation, but this would not guarantee…
joeb1415
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Are there some scattered point configurations that would yield bad interpolation results using Radial Basis Function (RBF) interpolation?

Is Radial Basis Function interpolation sensible to the scattered point configuration? I seem to be having problems for scattered points $(x_i,y_i)$ that are illustrated below: The values $f(x,y)$ can be generated using an fBm…
user13675
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Maximum of error in equidistant interpolation

Interpolating a function, to estimate the error, knowledge of the function $$\omega(x)=\prod_{i=0}^k (x-x_i)$$ with $x_i$ being the sampling points, is required. In the equidistant case, this would be: $$x_i=a+\frac{b-a}{k}\cdot i$$ Now I want to…
Hagadol
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grading accuracy of two lines

Possible Duplicate: Error measurement between given perfect 2D shape and freeform shape drawn by user I am programming (with vectors) an application which requires a user to draw line according to certain data. Then the user will click a check…
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Fast way to compute barycentric lagrange interpolation

Is there any fast way to compute the barycentric Lagrange interpolation using matlab?
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Non-linear ways to interpolate some data.

I'm trying to solve a problem where I have a large set of data points. Each data "point" has 8 independent variables (input) and 1 dependent variable (the output). I got this data through experimentation. Are there any non-linear ways that I can…
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Lagrange interpolation: Evaluation of error in interpolation

I was given the following nodes: $x_1=0$ $x_2=1$ $x_3=8$ $x_4=27$ and was asked to interpolate the Lagrange polynomial of the function $f(x)=\sqrt[3]{x}$ (meaning, I have the values: $(0,0)$,$(1,1)$,$(8,2)$,$(27,3)$ and need to interpolate the…
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