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Questions tagged [interpolation]

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

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5
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1answer
69 views

Eigenvalues and numerical eigenfunctions for similar differential operators

I am looking to numerically approximate the eigenvalues and eigenfunctions for a differential operator I am working with, assuming $\pi$ periodic boundary conditions. Namely, I define the function $...
0
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1answer
33 views

Find Unknown coefficient using Contour plot

I have I really complicated equation, but for simplicity lets assume my function is F(x,y,z)= ax+by+c*z, where a, b and c are some unknown constants. From experiments we know that at: x=3, y=2, z=1 ...
10
votes
2answers
488 views

Morphing between two functions

Assume we have 2 peaked positive functions f[x_] := Exp[-(x + 3)^2] g[x_] := 1/2 Exp[-(x - 3)^2/4] that look like Would it be possible to numerically find a ...
0
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0answers
32 views

Get R^2 value between interpolating functions and a list of points

I am looking to compare the degree of accuracy of a theoretical model by comparing my theoretical curve to my experimental data points. My theoretical curve is an interpolating function generated ...
0
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0answers
34 views

How to fit a spline (not interpolate) through points in 3D?

I have coordinates of points in 3D and want to fit a spline through these points. I found a least square approach for 2D case: https://demonstrations.wolfram.com/...
1
vote
1answer
81 views

How to fit spline through points in $ \mathbb{R^3}$?

I have coordinates of points that represent a curve (for example, helix or centerline of moebius strip) in $ \mathbb{R^3}$. I want to fit a Bspline through these points. How to do this in Mathematica? ...
3
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3answers
138 views

Interpolation[] gives negative values when all the initial data is positive

I have this data: ...
0
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1answer
26 views

I am having trouble with the Show[] section of this code

Question: I am unsure how to graph the interpolated graph with the regular graph on the interval [1,4]. Not even the Show line works about im pretty sure its written correctly. Clear["Global`*"] f[...
2
votes
1answer
38 views

Interpolating and subtracting two sets of data

I have a data set "data9k" with x varying from 0 to 365, and another data "data0" set with x varying from 0 to 365. But the x values for both data sets are not same but similar. I want to subtract the ...
0
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2answers
108 views

Non-linear differential equation with tricky variable dependence

My problem regards solving a differential equation and can be reduced to the problem of finding $f(x)$ such that $\frac{df}{dx}=\frac{dh}{df}$, with $h(f)$ a known function. I have this list of data,...
6
votes
1answer
140 views

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 ...
3
votes
0answers
49 views

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 ...
1
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2answers
48 views

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 ...
0
votes
2answers
55 views

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. ...
0
votes
1answer
132 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: ...
4
votes
3answers
127 views

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 ...
1
vote
1answer
32 views

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 ...
2
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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: ...
2
votes
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. ...
0
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1answer
53 views

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 ...
5
votes
1answer
58 views

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: ...
3
votes
2answers
175 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 ...
1
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2answers
78 views
6
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2answers
788 views

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: ...
4
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2answers
107 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 ...
3
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0answers
89 views

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 ...
0
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0answers
51 views

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 ...
7
votes
1answer
198 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. ...
1
vote
1answer
64 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}) ...
1
vote
1answer
55 views

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 ...
1
vote
1answer
70 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 ...
4
votes
2answers
133 views

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<...
1
vote
1answer
85 views

Interpolating 3D noisy data

I have some noisy 3D data that looks like this: ...
0
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1answer
34 views

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 ...
3
votes
0answers
82 views

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: ...
2
votes
2answers
129 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 ...
3
votes
1answer
55 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. ...
1
vote
1answer
64 views

Transpose Error

I have this code: ...
1
vote
2answers
72 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 ...
-1
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1answer
118 views
0
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0answers
63 views

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 ...
0
votes
1answer
121 views

Table and FindRoot of a two-variable interpolated function

I am having difficulty solving for the roots of the following interpolating function: ...
1
vote
1answer
41 views

The labels in the plot don't appear

the labels in the plot doesn't appear, axeslabel, plotlabel and plotlabels. ...
0
votes
0answers
40 views

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 ...
1
vote
1answer
67 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, ...
5
votes
2answers
221 views

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 ...
0
votes
1answer
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 ...
1
vote
0answers
47 views

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: <...
1
vote
0answers
28 views

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 ...
0
votes
1answer
82 views

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: ...