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# Questions tagged [interpolation]

Questions on the interpolation functions in Mathematica (InterpolatingFunction[], Interpolation[], ListInterpolation[], FunctionInterpolation[], InterpolatingPolynomial[], etc.)

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### Why FindRoot gives wrong answer for the roots of a vector interpolation function

I've tried to use FindRoot to find the roots of a vector interpolation function, but Mathematica is clearly giving me the wrong answer. What's going on here? Here ...
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### Animate does not work with Interpolating Function

I have an Interpolating Function T[t] (calculated as a solution to a DE). The following statements work just fine (where the a, r and tm have previously assigned numerical values and T[t] is an ...
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### Solving a second order pde from solution of another pde

I have solved the following pde numerically using NDSolveValue. ...
2 votes
0 answers
37 views

### Elegant way to handle a series of interpolation functions

In this post, I wrote a piece of code that can bypass singularities in numerical solutions of the first type of Painlevé ODE. The code is as follows ...
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1 vote
2 answers
85 views

### Arbitrary precision workflow

Please, consider the following MWE representing my code: ...
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3 votes
1 answer
66 views

### Integral of interpolation function is not evaluated

I am having a misunderstanding with Mathematica about integration of InterpolatingFunction. Consider this example: ...
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### Assign the result to the lists [duplicate]

I am following the solution of the mixing eigenvalues from Carl Woll's answer in this post. In the end, the eigenvalues are plotted using this formula ...
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1 vote
2 answers
86 views

### What is the best way to make an approximating function out of this list?

What is a good way to make an "InterpolatingFunction" from the following list represented on the Graphs? The small part that appears on the second graph is what causes the problems.The Goal ...
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5 votes
0 answers
54 views

### Interpolation on an unstructured grid with large aspect ratio

If you wish to interpolate on an unstructured grid then the solution is to use ElementMeshInterpolation from the Finite Element Method. I examined this here but now ...
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7 votes
1 answer
143 views

### Creating a Random T-Spline Instead of a B-Spline

I want to be able to create a function so that instead of BSplineSurface[pts], it would be TSplineSurface[pts,error]. I think it ...
4 votes
3 answers
178 views

### How to tell NDSolve to suppress creation of interpolation function on successful exit?

Update: I tried to work around DependentVariables, as suggested (thanks !) Here is the example from documentation for an ODE system, where InterpolatingFunction is created only for the variable x: ...
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### How can I find an inverse function of solution from NDSolve?

I have the following code. ...
3 votes
3 answers
97 views

### Integrate InterpolatingFunction times polynomial

Related: Integrating a functional of an InterpolatingFunction This has been here a decade ago and I'm sure is rather outdated. So same question: Suppose I have an InterpolatingFunction ...
4 votes
3 answers
191 views

### Finding a specific value from interpolating function

Suppose I have the given code: usol[t_, x_]:= NDSolveValue[{D[u[t, x], x] == Sin[x], u[t, 0] == 0}, u[t, x], {x, 0, 10}] and I need to find the value of ...
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2 votes
2 answers
140 views

### Shape of a boomerang

I want to create a physical pendulum in 2D with the shape of a boomerang. And first problem I met with was how to define a boomerang, so I could have a shape of it and use it to make my pendulum. Can ...
10 votes
1 answer
174 views

### Precision of interpolation function after exporting and importing

I've solved a differential equation using NDSolve with a large working precision prec. The output is a few interpolating ...
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2 answers
74 views

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1 answer
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### How to simplify this long notebook?

I have some large calculations I want to simplify them to reduce the number of lines as well as saving time. I have a quadratic equation based on C and I want its delta==0 and then solve it for "...
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### What can be improved in the following custom interpolation?

Consider some test data: a grid of x, y, and values of some function on this grid: ...
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4 votes
1 answer
220 views

### How to quickly sample points from the given PDF data?

Consider some data (distr.dat). It is a tabulated PDF: x, y, z, PDF[x,y,z], where x is some parameter (and the integral of ...
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1 vote
1 answer
72 views

### Extract boundary points of an interpolating function obtained by NDSolve

Given a set of coupled nonlinear equations I want to extract the boundary points that appears in the interpolation function obtained as an output to NDSolve function and then to define them directly ...
3 votes
2 answers
109 views

### Solving A System of Two Implicit Equations

I am solving a system of 6 equations, and I am interested to know the solution for different rhoBar values. Here is the input parameters: ...
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1 vote
3 answers
93 views

### Interpolating data which arent in the proper list form

I have some data which are structured poorly, and I want to interpolate them. This is the way they are structured: ...
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2 votes
0 answers
148 views

### Numerical Galerkin method with parametrized interpolation function

modified Here I try to realize a numerical fit (Galerkin method) using parametrized Interpolation function to fit examplary Exp[x] in a given grid. So far I tried <...
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1 vote
1 answer
92 views

### How to make a 3D interpolation function?

I have a following data, ...
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5 votes
4 answers
126 views

### Interpolation of missing matrix values

Problem statement I want to replace missing matrix values, denoted by an integer 0, with the Mean of their surrounding values. ...
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1 vote
0 answers
55 views

### Fitting experimental data to a plot with different x-axis paths

Given Mathematica code of eigenvalues in different variable-paths , I want to add experimental data in the path Gamma-X ; X-Gamma ; and M-Gamma . Here is the code : ...
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1 vote
2 answers
264 views

### How to interpolate an implicit function?

chi(t) is implicit function. The implicit function can be plotted by ContourPlot. Is it possible to obtain chi(t) explicitly using function interpolation? ...
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4 votes
3 answers
681 views

### How can I write the equation of the parabola passing through list of three points?

With three points a = {1, 2}, b = {2, 3}, c={-1, 5}. I tried to write the equation of parabola passing through given points like this. ...
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0 votes
0 answers
77 views

### Improving the curve of a quadratic spline interpolation

I have these data and I want to make a curve using quadratic spline interpolation. I am successful in computing the equations and plotting the curves. However, I noticed that the peaks of the curves ...
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1 vote
2 answers
95 views

### Finding the maximum amplitide quantitatively using interpolation

I have the following table data = Table[Sin[i], {i, 0, 10, 0.1}] // N And I plotted the data as follows, Now I want to know the value of each maximum with high ...
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0 votes
2 answers
59 views

### Interpolation function for data with repeating independent variable

I want to find an interpolation function for data in which the x-variable is repeated (example below). The repetition in data is natural and cannot not be eliminated. Can I somehow use ...
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0 answers
46 views

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5 votes
1 answer
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### Artifacts when interpolating on an unstructured set of 3D data

When doing an interpolation on an unstructured set of points it is best to use the interpolation method available from the finite element package. However, it is essential that some re-scaling is done ...
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3 votes
4 answers
314 views

### Volume of Region Contained by 3D Data Points

I have a dataset consisting of (x,y,z) data that describe a surface, and I need to find the volume of the region bounded by that surface. The data do not follow any mathematical equation, but the ...
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2 votes
0 answers
108 views

### Fractional derivatives (FractionalD) of an InterpolatingFunction to retun another InterpolatingFunction

Question I want to calculate the FractionalD of an InterpolatingFunction object, however, evaluating ...
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4 votes
1 answer
226 views

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0 votes
1 answer
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### Interpolation error to generate a two variable function

I am facing some issues with performing an interpolation. From the image, you can find the values in three columns, the 1st column is x, the second column is ...
0 votes
1 answer
38 views

### Volume of revolution with InterpolatingFunction

I have an $(x,y)$ dataset read in from a file. The data do not follow any sort of equation, but have the general shape of $y=x^2$. The data below are a placeholder ...
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25 views

### Problem with Piecewise function applying to matrix of polynomials

I have a matrix of a polynomial - function f f[t_, i_] := wielomianSpline[t, tx[[i]], wspfi[[i]]]; and I want to evaluate the ...
7 votes
3 answers
187 views

### FindPeaks in a 2d list and half values

FindPeaks is a nice little help. But it only works on 1D lists and tends to return half integer values for positions of the peaks which are ultimately very useless ...
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4 votes
3 answers
334 views

### Find the zero crossing in data [duplicate]

I have the following list. l = Table[Sin[i], {i, -4 Pi, 4 Pi}] // N which gives me the following data, ...
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4 votes
2 answers
79 views

### Does FunctionRange work with Interpolation?

$int = Interpolation[{{0, 0}, {1, 1}, {2, 2}}, InterpolationOrder -> 1] FunctionRange[{$int[x], x > 0.5}, x, y] returns ...
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1 vote
1 answer
74 views

### Interpolation of date-time data to fill in missing data for data sources with different time resolution

I have 2 data sources with different data acquisition rates. My first data source is a temperature measurement over time with a resolution of 1 s. My second source ...
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5 votes
3 answers
428 views

### InterpolationOrder creates a sharp valley even if I increase the number of points. How to have a smooth curve?

I have a set of data as the following ...
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1 vote
2 answers
153 views

### How can I interpolate a piecewise constant function?

Let the given set of points ...
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1 vote
2 answers
121 views

### How to correctly extrapolate function?

There is a function: ...
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0 answers
46 views

### RegionPlot from discrete data

I have a discrete set of plots in the form (x,y,v) similar to (this is sample data, the actual data contains 13000+ plots which can be downloaded from here ...
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1 vote
1 answer
174 views

### Interpolation with nearly duplicate points

I have data sets with very close values and I am getting the error that points are being duplicated. Here is a small part of one data set. ...
• 16.5k
4 votes
2 answers
286 views

### How to speedup the integration of a tabulated function?

The problem Consider some pre-generated list with coordinates x1,x2,x3,x4 and values of some function ...
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