# Tagged Questions

Questions on the numerical functions of Mathematica, implementing numerical methods and numerical computing with Mathematica.

101 views

### Classification problem using SVM methods

I am running SVM on mathematica and I a used this code with classes: ...
136 views

### Basic 2D convolution with mathematica

Can anyone tell me why the following keeps burning my CPU without ever producing the desired plot? ...
839 views

### Exponential fitting - isn't actually a BUG there?

There are many questions on this site about wrong exponential fitting in Mathematica but no one considers this well-known problem as a potential bug. Usually people suggest well-known workarounds ...
113 views

### Numerically Solving Helmholtz over the Rectangle - Why does this code only give eigenfunctions of the form $u_{m1}$ [closed]

I have been following the method for numerically solving the Helmholtz equation in this example (the answer by User21) and have come across two problems. I have been implementing the method for a 2x1 ...
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: ...
62 views

### Computing the logarithmic spectral norm rapidly

I wish to compute the logarithmic spectral norm of a square matrix $A$, which is defined by $$\mu_2[A]=\lim_{t\downarrow0}\frac{\|I+tA\|_2-1}{t}.$$ Hence, I simply code ...
35 views

### How do I numerically integrate the result of NDSolve if it depends on several variables?

I am trying to numerically integrate solution of NDSolve. I am trying to integrate my result of NDsolve in line 97 of my notebook, but am getting the error ...
96 views

### How to fit parameters, not functions?

Given a set of parameters ...
86 views

### Solving numerically a system of equations using different methods

I will use, as an example, the simple Henon-Heiles potential ...
76 views

### Paramter Scans and $\chi^2$ Test in Mathematica

Is there any in-built function or a recommended package that enables one to find, say, 10 Parameters, which are used as boundary conditions in NDSolve, that minimize $\chi^2$? ...
45 views

### Differential equation for a list with parameter dependent function

I am having a differential equation: y' = (1 - y) - f[y, mu] y; f is a hysteretic function that depends on y and on the derivative of y: ...
71 views

### Integrate over FindRoot solutions

I have a function of bivariate normal PDF and its marginals defined as ...
281 views

### Trouble with shooting method for a 4th-order stiff ODE

The ODE I need to solve is $$\left(y^3y^{\prime\prime\prime}\right)^\prime+\frac{5}{8}xy^\prime-\frac{1}{2}y+\frac{c}{y}=0$$ where $\prime$ denotes differentiation, $c$ is a constant and $0<c\le1$....
69 views

### LinearSolve on non-square matrices?

I just came across a strange behaviour for LinearSolve (on Mathematica 8.0.0.0). Consider the following definitions: ...
205 views

### Maximized value of a function as an additional constraint on a variable

I want to maximize a function $f(b, h)$ with respect to its arguments and subject to some additional constraints. If these constraints are satisfied, $f$ is increasing in $h$. I then want to find an ...
396 views

### Wrong result of simple math calculation. Is it possibly a bug of the program? [closed]

I encounter the following issue accidentally (shown in the screenshot) which is very odd to me. The output[4] and [5] is obviously wrong. But with the input value of 991.91, it turns out to be right (...
72 views

### How does Plus work on machine precision Real arguments?

I thought Kahan's summation method would make a nice example for students to use to think about round-off error [W. Kahan, Pracniques: Further Remarks on Reducing Truncation Errors, Commun. ACM 8  (...
116 views

### How can I increase the precision of my computation?

How can I increase precision up to 15 digits for the results (EC, and that of FindRoot) computed below? ...
141 views

### Chopping matrix elements, real or imaginary

An undesired shape of a matrix has the following form: which is created by ...
208 views

105 views

### Unexpected behavior from Accuracy

This is my code Table[With[{x = 10^n + 1/17}, N[x, {Infinity, 5}]], {n, 0, 5}] // Column Or like this ...
49 views

### System of ODEs - NDSolve issues

I am a self-taught beginner trying to use Mathematica for the first time. If you wouldn't mind, I would like to ask for help with the code I am working on as I keep running into multiple issues when ...
107 views

### Compilation, square roots, and integers

After looking at this question, particularly this answer, I wrote my own performance test, using the two functions ...
131 views

Bug introduced in 10 and persists through 10.3.1 or later I created this InterpolatingFunction, and NIntegrate gives an ...
400 views

### Bug: Wrong results from NSolve on coupled polynomials. WorkingPrecision->Automatic fails

OP UPDATE: I received an email from WR on 1-18-2016: "...It does appear that the NSolve function is not behaving properly in this case and I have forwarded an incident report to our developers with ...
58 views

### Error message when using a compiled function in NSum [duplicate]

Below is a simple example to illustrate the problem test = Compile[{{n, _Integer}}, n] Now, Table works fine ...
71 views

### EvenQ not working properly on IntegerPart[real number]

Something fascinating is happening at the moment. ...
90 views

### singularity in boundary value problem

I am trying to solve a non linear differential equation with variable parameter. ...
608 views

### more numerically accurate inverse matrix

I encountered the following matrix mat = {{2, 2.161209223472559 + 1.682941969615793 I}, {2.161209223472559 - 1.682941969615793 I, 2}} and ...
45 views