# Tagged Questions

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

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### How to use interpolating functions in NSolve with a piecewise function?

I have a system of two non-linear differential equations that are piecewise, the solutions of which I would like to use to obtain the values of a third variable that is also piecewise. I have trouble ...
85 views

### Extract one dimension from an n-dimensional InterpolatingFunction

How can I extract a single dimension from an InterpolatingFunction? As an example: ...
139 views

### interpolating a smooth closed surface to a non-uniform data set (ListSurfacePlot3D)

I want to generate a smooth coloured surface from a discrete set of points of the form {x,y,z,F} using the ListSurfacePlot3D. My data set is quite non uniform; the ...
51 views

### Taking the derivative of the complex conjugate/absolute value of an interpolating function

I have following code: ...
136 views

### 2D interpolation

Consider following series of functions Do[f[k][w_] = Exp[-(w-Sin[k])^2], {k, 10}] depicted as Let us tabulate and interpolate them ...
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### NDSolve with an interpolating function in Piecewise

Again I have question I hope someone can answer. I made a very simple example illustrating my more difficult problem. I want to solve a differential equation numerically with a conditional in the ...
59 views

### Getting FindRoot::nlnum when trying to find root of an Interpolating function [closed]

I want to solve a system of differential equations and find a point where the solutions cross. So four steps: 1. Solve the system of differential equations: ...
63 views

### Merging of multiple 3D plots with Show using unified ColorBar

This question follows my initial question that can be found here. I created the following 4D plot (3 spacial coordinate + color) by interpolating points separately. The full data (1.4Mb) can be ...
195 views

### Produce a spline from a set of {{x, y}, z} points and get its parameters/expression

I have produced a set of points in a variable of the type {{x1, y1}, z1},{{x2, y2}, z2}, ,... }, where {x, y} should be the ...
237 views

### Smooth 3D plot with colour of scattered data

I have a set of scattered 3D points with coordinate (x,y,z) and an intensity associated with it. I would like to do a smooth surface with the intensity being represented by the colour. My points ...
119 views

### Integrating an interpolating function

I have been using the following NDEigensystem command to generate the eigenfunctions of the laplacian with a square domain: ...
84 views

### Help with Time-Seried dataset

I can't seem to figure out the best way for directly inputting interpolated values into a dataset. I turn to your expertise for guidance. So, I have a multi-year time-series dataset. Column 1 is time ...
58 views

### Numbering indices / array element positions while creating an array (using 3 argument form)

I am new to Mathematica and trying to create a list that I can use within the InterpolatingPolynomial function. e.g. ...
90 views

### Interpolation of a border between regions in ListDensityPlot

Let's say there is a scalar field dependent on two coordinates {x,y}, so a set {x, y, f}, and I use a ListDensityPlot to plot it: ...
101 views

### Plotting the solution of a differential equation with its derivative [closed]

The question requires checking of numerical solutions to a differential equation by substituting in those solutions. The original equation is as follows; ...
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### Export NDSolve data

I have calculated a solution of a system of differential equations using NDSolve and generated a plot. How could I extract the data of the solutions? The input is ...
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### How to exchange interpolating function results of NDSolve between different platforms?

For example, I have a interpolating function solution by NDSolve in a windows x64 platform and want to share the result to users in other windows x86. I tried the DumpSave and ".mx" binary format, ...
35 views

### Why does ListInterpolation convert integers to reals in the internal representation?

This problem is mentioned in my self-answer here. Here is an illustration of the problem: ...
329 views

### Finite Element Method and ElementMeshInterpolation issue in v10.3

Bug introduced in 10.3 I recently installed Mathematica v10.3 and checked a project I was working on few months ago under Mathematica v10.1. In this project I solve a PDE with ...
149 views

### Using ListInterpolation to get a vector-valued function

I wanted to construct a ColorFunction from an image, so I tried ...
126 views

### Interpolation of data on a 4D grid

I have a 4D grid ...
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### Weird behaviour for a vector InterpolatingFunction inside an NDSolve

I have run into some weird behaviour on the part of NDSolve which I find pretty bizarre and which I would like to understand better. Suppose, for the sake of ...
141 views

### Getting an explicit representation of the function returned from Interpolation [duplicate]

I am using Interpolation to get an InterpolatingFunction that fits a set of points. For example, ...
109 views

### Combining two list function (Is it the best way?)

Suppose I have two list, ...
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### Interpolate the discrete list into continuous function

I have a data whose list plot shows up following graph I would like to interpolate the missing data and make the function continuous but for particular x-coordinate there is multiple values of $y$ ...
188 views

### Unexpected view of the Comsol result when I postprocess it in Mma

I simulated some nonlinear PDE using Comsol. Here one can find the results u=u(x,y) in the form of an Excel table with the terms ...
128 views

### FindRoot of interpolating function from NDSolve

I am having issues finding the root of an interpolating function obtained from NDSolve. For example: ...
161 views

### Smooth initial data

I need something that produce pseudorandom smooth initial data for modelling phase separation equations (Cahn-Hilliard and simular). Generator code for now: ...
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### How to define InterpolatingFunction on a variable set of points?

I would like to define an InterpolatingFunction to which data points are transferred as a parameter, e.g.: ...
188 views

### Bug? Problem with derivative of interpolating function from FEM

Bug introduced in 10 or earlier and fixed in version 10.4 I am really not sure if this is a bug or I am missing something very trivial. QUESTION: What I am missing in order to obtain the partial ...
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### Convolution of interpolated data with function doesn't work

I need to convolve one function with interpolated data: function: av1 = 1.3888*(12/20)*10^8; bv1 = 2.5; tr5[t_] = Exp[-(av1*t-bv1)^2]; Data: ...
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### Interpolation function way off

I have a simple list of data points to which I would like to fit an interpolation function. However, the results given by Interpolation[] gives an oscillating function which is not warranted by the ...
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### Gradient of interpolated 3D data in mathematica 9

tt = Flatten[Table[{x, y, z, btot[x, y, z]}, {x, -1, 1, 0.1}, {y, -1, 1,0.1}, {z, -1, 1, 0.1}], 2]; ff = Interpolation[tt] Till here it is working fine as it is ...
123 views

### Interpolation of a multivariate function with duplicated 2D abscissa points

I want to interpolate a function q[a,b] I have a data file which has the form {a,b,q} a sample is following ...
63 views

### How to perform multi-variate Interpolation from discrete data in a text file [closed]

I have a table of data of 4 columns in text file. x y z w This is basically $(x,y,z)\rightarrow w$. How can I use an interpolation function in Mathematica to figure out an equation $f$ of 3 ...
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### Interpolation of 4D data on a triangular grid

I need to interpolate a function defined on a triangular surface (grid). The grid is defined as ...
131 views

Bug introduced in 10 and persists through 10.3.1 or later I created this InterpolatingFunction, and NIntegrate gives an ...
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### How to fix the error InterpolatingPolynomial::ipdup: The abscissas are not distinct [closed]

I'm trying to plot the function Abs[InterpolatingPolynomial[..] - f[x]] where f is a function. I receive the error: InterpolatingPolynomial::ipdup: The ...
84 views

### How to use BSplineFunction for calculating derivative

I have a set of data like the following data = {{x1,y1},{x2,y2},{x3,y3},......} Now I use ...
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### define function with 3d discrete points and find corresponding value from that function [duplicate]

Now I have a set of 3d discrete points in the form of {x,y,z} and want to interpolate them and define them into a function making x and y as the variables. Subsequently read corresponding values of z ...
176 views

### How to take derivative of a interpolated function inside the module

When handling derivatives of a interpolated function, I often use the following function makeDeriv[f_InterpolatingFunction] = D[ f[x], x] Then, I can define ...
68 views

### Using the InterpolatingPolynomial function

How can I find the interpolation polynomial for the function $f(x) = \frac{1}{1+2x^2}$ with interpolation knots $x_k = 1 + 0.2k , k=0,1,...,6$ using the ...
47 views

### Find interpolation polynomial using newtons formula

I found this program for calculating the interpolation polynomial using Newtons formula. This function takes as input data points and returns a polynomial. For example: I want to find the ...
140 views

### Non-rectilinear integration of InterpolatingFunction

Bug introduced in 7 or earlier and persisting through 10.3.1 [CASE:3487737] I have a 2-d array that I would like to resample into a different coordinate system and integrate along one of the new ...
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### Data Interpolation of deaths by date

I am working with an ebola dataset from Guinea, 2014:(http://currents.plos.org/outbreaks/article/estimating-the-reproduction-number-of-zaire-ebolavirus-ebov-during-the-2014-outbreak-in-west-africa/). ...
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### Accurate Integration of 2D interpolating function with weighting

I want to integrate a 2D interpolating function received from NDSolve[]. To illustrate my problem I will give a simple example: ...
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### InterpolationOrder has no effect on ListContourPlot when the data is of the form {x,y,f[x,y]}

This is related to the issue brought up here, if you want to mark it as duplicate feel free to do so, but it is slightly separate. Take two sets of data, identical except for the form, ...
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### List of points of an increasing sine function

I'm trying to obtain a list of the points of an amplitude-increasing sine function. I would like to give a certain value for input, e.g. 0.5. Sine will start increasing and decreasing from this point, ...