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

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4
votes
2answers
131 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
57 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
41 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
135 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
74 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
61 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: ...
5
votes
0answers
70 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
66 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
254 views

Finding intersection points of two graphics

I am drawing a curve from a list using: ...
0
votes
1answer
60 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
95 views

Get value from InterpolatingFunction

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

Problem with MissingDataMethod [closed]

Given v = {2, 1, Missing[], 5, 7, 4}; I use EventSeries to replace the missing value with its predecessor ...
4
votes
3answers
181 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
96 views

SystemException with Interpolation

Consider the following sample code Interpolation[{Range[20], 2*Range[20]}]; ...
3
votes
0answers
91 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
45 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
94 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
88 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
138 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. ...
5
votes
1answer
94 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
116 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
127 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
73 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 ...
7
votes
1answer
105 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
113 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. ...
8
votes
3answers
270 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
128 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: ...
3
votes
1answer
97 views

Finding the attractors of the vector field constructed as the gradient of an interpolated 3D scalar field

I have a list of data existing as {{{x, y, z}, f},...} from which I construct a 3D interpolation function using Interpolation[ ]. I am able to construct a vector field from the gradient of this scalar ...
1
vote
0answers
58 views

Continuous integration of a tensor function using discrete density values

Hei, I am wondering is it possible to implement continuous integration using Integrate() of a fourth order tensor with discrete density values. ...
3
votes
1answer
112 views

Interpolation of ListContourPlot3D, Volumetric data (cube file)

I know there are lots of information about this on stack exchange! Data interpolation and ListContourPlot InterpolationOrder for ContourPlot Unfortunately I was not able to find a proper way to ...
8
votes
3answers
102 views

Indexed and array-valued interpolations

Bug introduced in 10.1 or earlier and persisting through 10.3.0 or later Using Indexed on an InterpolatingFunction leads to ...
5
votes
2answers
138 views

FunctionInterpolation and Which combine badly

Update 2: Got two solid answers, but had trouble implementing one, and found the other could only save me computation time by sacrificing accuracy. So I chose neither as an official answer, but ...
6
votes
1answer
171 views

How to avoid creating negative values when using Interpolation?

I'm having some problems with Interpolation. I'm trying to interpolating some measurements data into mathematica. But using Interpolation will create some negative data, which is actually not possible ...
3
votes
1answer
74 views

Table generation with SetDelayed function [closed]

I would like to understand why the following two outputs differ: Let us define the following data set: ...
1
vote
1answer
75 views

How do I restrict the range of an interpolating function in NDSolve?

I have a numerical solution for a differential equation. I know that the gray dotted solution is unphysical. Is there a way I can tell mathematica to ignore the gray dotted solution (e.g. restrict the ...
1
vote
1answer
59 views

Can list interpolation be made listable? [closed]

I have 8 sets of 2D-data that I want to each interpolate with ListInterpolate, because it is a very efficient command. The complete data are therefore in a 3D ...
2
votes
2answers
309 views

Interpolation showing noise in “non-noisy” data set

Stuck trying to get the interpolating function to match the (what I thought was a) smooth point set, how best to deal with this? Many thanks. ...
4
votes
2answers
271 views

NMinimize Constraints on Interpolating Functions

I have the following piece of code and am trying to use NMinimize (the last line in the following chunk of code) to minimize ...
7
votes
1answer
213 views

Smoothen the curve found by EdgeDetect

It seems that curves found by EdgeDetect always persist $C^{0}$ continuity only. Consider the following example: ...
0
votes
0answers
18 views

Question regarding derivation of Interpolation functions [duplicate]

I am new to Mathematica. Can someone explain what is the difference between the second and third input (54 and 59) in following example (got from Mathematica site). In[52]:= ysol = ...
3
votes
0answers
101 views

How to find the best fit for given input data? [closed]

I have the following data: ...
6
votes
2answers
212 views

What's the difference between Interpolation[pts, Method -> Spline] and BSplineCurve?

Last month, I answered a question about spline interpolation,please see here Now I do the following operations ...
2
votes
3answers
87 views

InterpolationOrder 2 or more in ListLogLinearPlot

I'm using the function ListLogLinearPlot, but the plot is to square, i would like to have InterpolationOrder 2, but there is not ...
-1
votes
1answer
139 views

Multidimensional Interpolation with 3 independent Variables with modfied data set [duplicate]

I have four column data with first 3 column denoting x,y,z and fourth column energy. x variable is actually angle. Now I want to interpolate over all three indepdent variable (x,y.z) with ...
17
votes
1answer
315 views

How can I smooth a 3D surface generated by RegionBoundary?

I have a set of points that belong to the surface of an object. I would like to approximate a surface to which I can compute the distance. of other points. With the nice code of this post, I was able ...
9
votes
2answers
128 views

Finding self-intersections of a closed curve represented by an interpolation function

I've been trying to find particular simple closed curves on a plane. ...
3
votes
3answers
309 views
3
votes
0answers
88 views

Defining a region from combination of data and geometric region

I would like to define a region in (x,y) by combining the region RegionPlot[ ImplicitRegion[ Sqrt[x^2 + y^2] <= 0.99, {{x, 0.01, 0.99}, {y, 0.01, 0.99}}]] ...
13
votes
3answers
778 views

Subtracting two plots from each other after shifting one

I have the following lists representing energy spectra that need to be subtracted from each other to produce a difference spectrum. ...
9
votes
1answer
156 views

Kernel Crash while using “ValuesOnGrid” method of InterpolatingFunction

Bug introduced in 10.0.0 and fixed in 10.2.0 I was experiencing some kernel crash while using "ValuesOnGrid" method of an ...