Questions tagged [interpolation]

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

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Multiplying interpolations

I have two interpolated data sets data1 and data2. I want to create a function that returns the intepolations multiplied. For instance, func[x] = data1[x]*data2[x].
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How can I accelerate repeated interpolation of a very large dataset?

I am solving a 4D time-dependent PDE using a discretization method. My query is not about solving this; because I am doing it in the following code. The code is OK and it works fine. My main problem ...
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Extracting part of an Interpolating Function [closed]

I get an InterpolatingFunction, call if F1, as a solution to NDSolveValue. I then need to do further operations on this function. However, I only need to work with a small part of the domain of the ...
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How can I convert a matrix of 3d experimental data into a 3d list which can be interpolated in a f(x,y) function

I have a 3d experimental *.txt data with the form: y1 y2 y3 x1 f(x1,y1) f(x1,y2) f(x1,y3) x2 f(x2,y1) f(x2,y2) f(x2,y3) x3 f(x3,y1) f(x3,y2) f(x3,y3) I need to ...
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Better fit for points with exaggerated deviations

I used the InterpolatingPolynomial function to get a polynomial that meets my points. But I noticed that there is a deviation in the final intervals. ...
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1answer
115 views

Is it possible to fit such a large range plot in mathematica?

I am trying to solve the coupled differential equation numerically with Mathematica. But the range of values are large so mathematica cannot give correct plot. Here is the code: ...
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questions about InterpolationOrder

I have a function $C_0(x)=e^{-(x-2.5)^2/2.0}$ which is differentiable to infinite order. I want to approximate the function with Interpolation such that it is smooth until 10th derivative. Here is ...
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NSolve with Interpolation function

I am trying to apply NSolve to an Interpolation function which I have evaluated before. For a function of 1 argument everything works out but as soon as I try to apply the procedure for a function of ...
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2answers
150 views

How to use NDSolve with limited RAM?

How can I use NDSolve when running out of RAM? The code I am implementing: ...
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1answer
41 views

Narrowing the range of an interpolating function while keeping integral the same?

Consider an interpolating function derived from some data, e.g. ...
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Factor to measure polynomial fit

I am trying to use InterpolatingPolynomial to fit a polynomial to a given set of points representing a relationship between two variables. I would like to find a ...
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Weirdness with Interpolation of data and InverseFunction

Bug introduced in 8 or earlier and persisting through 12.0 Something strange is happening with this list of data: ...
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168 views

How do I restrict an interpolated function to only take values > 0?

I have a list of points which looks like this when plotted with Joined -> True: I'm interested in the area under the curve with x-axis > 0 as a ratio to the ...
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Integration of Interpolated function take an unacceptable amount of time

I have a simple integration which, when using an interpolation function, is taking too long to calculate: ...
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92 views

Plotting perpendicular lines to a contour plot (electric field from equipotential curves)

I'm currently working on a experiment about Electric Fields and Equipotential Curves. The problem is that I want to plot (estimate) the curves of electric field using the fact that every one of these ...
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How do I truncate an interpolating function?

I have a very large interpolating function and want access the function at one point in time. I am running out of RAM running ...
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How to apply the utility Packages for Numerical Differential Equation Solving

I have solved two coupled equations with {Solf, Solg} = NDSolveValue[eqns, {f, g}, {x, 0, L}, {t, 0, tmax}] and want to extract the computational grid ...
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177 views

How do you interpolate outside the range of data?

I've got a simple interpolation function using data from an external program. For values above 3,000, the function reaches a limit. ...
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1answer
52 views

Regression to fit data with an integral equation

I have a set data and I know that this data are best fitted by the following equation, assuming that f($\tau$) is a log normal distribution and $M_{eq}$ = 1.5: $M(t,\tau)= M_{eq} \int (1-e^{-t/\tau}) ...
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Interpolating data from Excel

Sorry for the probably mainstream question, but I have not found the answer I was looking for yet. I have this Excel file: https://drive.google.com/file/d/1UhkYdoaqXQIsf6opOx-EBgG7xPxxHga3/view and I ...
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1answer
67 views

How to make that interpolation?

I have the following dataset: SetDirectory[NotebookDirectory[]]; TableSpectrum = Import["spectrum.dat", "Table"]; I want to make the interpolation. However, when ...
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Trying to build a function to compute divided difference for arbitrary list of points

As the title says Im trying to build a function to compute divided difference for arbitrary list of points. The divided difference of a set of points $\{(x_1,y_1),\ldots, (x_n,y_n)\}$ where $x_j<...
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1answer
83 views

Interpolating 3D noisy data

I have some noisy 3D data that looks like this: ...
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1answer
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TargetUnits aren't working as expected on an InterpolatingFunction

Short version: My understanding of the use of TargetUnits in a Plot statement is that if the function being plotted has units, MMA will attempt to convert the output of that function to the unit form ...
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How to use an interpolating function as an intial condition for a PDE? [closed]

I want to be able to approximate a PDE, but my eigenfunction is an Interpolating function. Is there a way I can use an interpolating function as an initial condition in the PDE. For Example: ...
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2answers
121 views

Fitting two-dimensional data

For this question, I cannot use random sample data. So the actual data can be found here. The data file contains three columns, where the first two are the coordinates $(x,y)$, while the third is the ...
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1answer
51 views

Problem with interpolating function returned by NDEigensystem

I'm trying to evaluate interpolating function returned by NDEigensystem at a point but Mathematica won't evaluate it. ...
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1answer
61 views

Transpose Error

I have this code: ...
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70 views

Interpolating missing data

I have a data set that contains data of the form (x0, y0, f1, f2, i1, i2, i3). The (x0, y0) are the coordinates, while the values f1 and f2 are real numbers (i1, i2, i3 correspond to some integers ...
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InterpolatingFunction in NSolve

I'm trying to get NSolve to solve a simple system of equations. It makes use of various interpolating functions (for thermodynamic properties). I can solve the system outside of NSolve by ordering the ...
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1answer
120 views

Table and FindRoot of a two-variable interpolated function

I am having difficulty solving for the roots of the following interpolating function: ...
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1answer
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The labels in the plot don't appear

the labels in the plot doesn't appear, axeslabel, plotlabel and plotlabels. ...
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Obtaining the equation type of an interpolated function

I used InterpolatingFunction on a set of points. How can I know the type of that equation ? (polynomial, sinusoidal, logarithmic,etc...). I am looking for a general case answer. Here is an example ...
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1answer
63 views

Mesh quality error with interpolation of table

I am trying to interpolate a table of the following form. {{x1,y1,z1},{x2,y2,z2}...} Where z depends on x and y, and x ranges from 0.01 to 1 in steps of 0.01, ...
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How can I fit a function onto a histogram?

SampleData = RandomVariate[RayleighDistribution[3], 5000]; Histogram[SampleData] This creates a histogram that (in my case) looks something like this: I want to ...
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39 views

How to obtain the correct interpolation for the following data?

I have a dataset DistrTemp.dat. It represents a set of data in the form {{x,y,z,f[x,y,z]}}. Here, x defines a system, while ...
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Interpolation of multidimensional data: some domains are lost

I am trying to make a reasonable interpolation of a dataset having the form dataset = {{x1,x2,x3,f[x1,x2,x3]},...}. I to the interpolation in the following way: <...
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Extra interpolation in ListPointPlot3D

I'm trying to plot a 3D surface using ListPointPlot3D and it looks almost right, but for some reason it's trying to connect points that should not connect. I think it's confused because the surface is ...
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1answer
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Interpolation function error: The quality of the underlying mesh is too low

Consider a dataset BplustoPiXlight.dat (alternative link). I import it and try to interpolate: ...
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BSpline vs natural spline [closed]

The BSpline in mathematica is defined mathematically here. These BSplines constitute basis for any Spline. But how do I define natural splines in mathematica, i.e. splines that are linear left of the ...
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68 views

Interpolation works slowly

Consider the following code: ...
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ElementMeshInterpolation and C1 splines

I am trying to use NDSolve`FEM`ElementMeshInterpolation on a triangular structured grid constructed from a Delaunay triangulation with zero area triangles dropped. ...
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Parallel evaluation of RandomVariate for an InterpolatingFunction

I need to generate a lot of point according to a given distribution. I don't have an analytic form of this distribution so I am using an InterpolatingFunction of ~100 points computed numerically. I ...
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Computing the volume enclosed by revolving a B-spline

I would like to ask if it's possible to get a function from a B-spline curve besides InterpolatingPolynomial[...]. I'm trying to use the function to compute the ...
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2answers
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Calculation using interpolating function

Say I have two replacement rules in terms of interpolating functions. ...
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1answer
52 views

2D interpolating function doesn't reproduce data

I have the following 2D data set: ...
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1answer
64 views

Problem with fit

I am trying to find a proper matching function for the following data set: ...
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1answer
178 views

Meaning of InterpolationOrder -> All for multidimensional interpolation

What specific method does Interpolation use for unstructured multi-dimensional data when we set InterpolationOrder -> All? ...