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

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5
votes
2answers
60 views

Using ListInterpolation to get a vector-valued function

I wanted to construct a ColorFunction from an image, so I tried ...
4
votes
1answer
79 views

Interpolation of data on a 4D grid

I have a 4D grid ...
0
votes
1answer
42 views

Bilinear interpolation [closed]

I have a matrix with n rows and m columns. I would build a two-variables function which interpolates these points (it's a bilinear interpolation problem). How can I found a two variables function ...
3
votes
0answers
50 views

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 ...
6
votes
2answers
118 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, ...
2
votes
1answer
97 views
0
votes
1answer
45 views

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 $y$ ...
9
votes
2answers
98 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 ...
2
votes
1answer
61 views

FindRoot of interpolating function from NDSolve

I am having issues finding the root of an interpolating function obtained from NDSolve. For example: ...
2
votes
3answers
71 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: ...
0
votes
1answer
45 views

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.: ...
7
votes
1answer
111 views

Bug? Problem with derivative of interpolating function from FEM

Bug introduced in 10 or earlier and persists through 10.3.1 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 ...
0
votes
1answer
46 views

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: ...
9
votes
1answer
274 views

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 ...
-1
votes
2answers
64 views

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 ...
2
votes
1answer
71 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 ...
2
votes
1answer
55 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 ...
0
votes
0answers
51 views

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 ...
0
votes
0answers
89 views

Find the (gaussian) function to fit a series of points?

I have a series of measurements for concentration of pollutant on a river C(x,t) where x is the location on the river and t is the timestamp. When plotted these data suggests a bell curve like Gauss ...
4
votes
1answer
125 views

Saved InterpolatingFunction behaving badly

Bug introduced in 10 and persists through 10.3.1 or later I created this InterpolatingFunction, and NIntegrate gives an ...
1
vote
0answers
47 views

How to fix the error InterpolatingPolynomial::ipdup: The abscissas are not distinct

I'm trying to plot the function Abs[InterpolatingPolynomial[..] - f[x]] where f is a function. I receive the error: InterpolatingPolynomial::ipdup: The ...
5
votes
1answer
56 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 ...
0
votes
1answer
26 views

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 ...
4
votes
2answers
118 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 ...
3
votes
1answer
50 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 ...
1
vote
0answers
34 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 ...
9
votes
1answer
129 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 ...
3
votes
0answers
68 views

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/). ...
1
vote
1answer
52 views

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: ...
4
votes
0answers
57 views

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, ...
0
votes
2answers
64 views

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, ...
5
votes
4answers
241 views

Finding intersection points of two graphics

I am drawing a curve from a list using: ...
0
votes
1answer
54 views

Getting numerical values from integrated interpolating function [duplicate]

I have a list of data. I integrate them with interpolation. Lets say is the following: InterpolatingFunction[{{0.01, 4.82}}, <>][x] However, is that ...
1
vote
2answers
91 views

Get value from InterpolatingFunction

I'm trying to find My[t], Mx[t] and Mz[t] values when evaluated at ...
3
votes
0answers
51 views

Problem with MissingDataMethod

Given v = {2, 1, Missing[], 5, 7, 4}; I use EventSeries to replace the missing value with its predecessor ...
3
votes
3answers
161 views

How to read the intersect corodinate of two lines from the ListLinePlot?

Suppose I have two curves intersect at some point, how can I read the coordinates from the graph, not read by eye, but find it with more precision by computer. For example, here are two lists created ...
3
votes
1answer
85 views

SystemException with Interpolation

Consider the following sample code Interpolation[{Range[20], 2*Range[20]}]; ...
3
votes
0answers
89 views

Data smoothing in three dimensions

I have data with statistical fluctuations of the form $f(x_i,y_i)$ over a discrete grid. I now need the values of $f(x,y)$ also at points other than the grid points. That can be achieved by ...
2
votes
1answer
39 views

ndsolve interpolatingfunctions not shown/evaluated

Using this technique from Simon, I want to solve a matrix differential equation with a matrix that contains an explicit time-dependence(our variable), but I want to be able to solve this problem for a ...
0
votes
0answers
90 views

Absurd solution by LinearSolve

I am trying to find curve that passes through all the data points.To do this i am doing interpolation using LinearSolve. No. of equations vary from 1000 to 3000. LinearSolve gives me values of ...
1
vote
0answers
84 views

Determining the order of continuity (smoothness) of a function

Is there any method to determine the order of continuity of a function (just like an interpolant) over a given domain, or at least determine the continuity on a given order? For example, according to ...
1
vote
1answer
82 views

Working with Interpolating Functions

I have two sets of data that are not regularly sampled, and I want to produce a quantitative measurement of how similar they are while fitting them with an $x$ shift and $x$ and $y$ scaling. ...
4
votes
1answer
87 views

How to get `FindCurvePath` to return only one list

As you can see below, FindCurvePath returns only a part of the list, resulting in a partial interpolation. I would like to interpolate all the points. Complete ...
3
votes
1answer
91 views

Repeated interpolation for 3D unstructured grid -> Optimization

Trying to perform mesh-to-mesh 3D interpolation on unstructured grid. Mesh size is about 200k nodes. Painful thing that interpolation shoud be repeated ~1000 times (different thermal map) on the same ...
2
votes
3answers
98 views

Extract function from a parametric interpolating function

I've read the answers of How to make use of an interpolating function outside of Mathematica?, Interpreting the interpolating function and saving data to plot with external program, Extracting the ...
3
votes
0answers
66 views

Diagonalisation of equations for NDSolve

I have a linear matrix differential equation and I wish to speed up evaluation by diagonalising using eigenvectors. There is an example in Help for finite elements under "swinging beam" that is ...
6
votes
1answer
88 views

How do I reverse the X-axis on a ListDensityPlot?

I want to use ListDensityPlot on a dataset containing a few (~600) triplets and I would like to reverse one of the axes. Sadly, the workaround involving the ...
4
votes
1answer
91 views

How to get coordinate from spline interpolation

Hi, I would like to find 10 coordinates between each points of this spline interpolation. I have done some research, but cannot find an appropriate answer. Any help will be appreciated. ...
7
votes
3answers
247 views

Linear interpolation of elements in a list to generate new list

For a list of any given length, I want to generate another list from it adding elements which are mean of the consecutive elements, in between the elements, of the original list. For example: ...
2
votes
2answers
123 views

How to store an InterpolatingFunction? [duplicate]

Assume I have obtained an InterpolatingFunction, say, as the result of solving of a differential equation, say, this one: ...