# All Questions

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22 views

### Python scipy NLLS optimization : Parameter estimate hugely off, but the visualisation looks fine

I don't have almost any experience in data modelling so I would really appreciate any input! I have to fit some models to my data - below you see the raw decay, the smoothed version that is actually ...
58 views

### Generating structured paraboloid using gmsh

I am trying to get the structured mesh as shown in the figure. I have used the transfinite surface and curve to achieve the same. Though I get the structured mesh but I do not know how to do for body-...
36 views

### Generating Rvs for a given PDf in python

Two random variables $X$ and $Y$ are distributed according to \begin{align} f_{XY}(x,y)= \begin{cases} x+y & 0\leq x \leq 1, 0\leq y \leq 1 \\ 0 & otherwise \end{cases} \end{align} I ...
47 views

### How to reduce computational time in DDE simulation on Matlab

I need to simulate a network of nodes. The weights of the edges are being given in a matrix . Due to the non-zero distances between the nodes, we consider time-delays, which are computed given the ...
81 views

### ODE45 and a variable that assumes multiple values during the timespan

I have tried in different ways to see what happens to voltage V and gating conductances m, n and h when, at time step x, current I switched from 0 to 0.1, and then at time step x + n it gets back to 0....
98 views

### Implementation of Source Panel Method as Described in Katz Plotkin Book

I am currently trying to implement Source Panel method as described in Katz and Plotkin in Low Speed Aerodynamics. I have successfully implemented two previous methods. However, I am fully blocked on ...
80 views

### plotting $F=K \frac{q_1 q_2}{r^3}$ in python

I tryin to plot the position of electron in the hidrogen atom by Coulomb's law, $F=K \frac{q_1 q_2}{r^3}$ This is mi code ...
77 views

77 views

### Is the sine function periodic in $x$ or $y$?

I know sine is $2\pi$-periodic, but some people say the motion is "periodic in..." Would it be periodic in $y$? If we move along the $x$-axis, the function values $y = \sin(x)$ will repeat, ...
127 views

### Plotting the difference between an exponential and its Taylor expansion as a function of number of terms?

I'm terribly green, please forgive me. I need to plot the difference between a chosen calculated Taylor expansion $e^x=1+x+\frac {x^2}{2!}+\frac {x^3}{3!}+\frac {x^4}{4!}+\frac {x^5}{5!}$... and the ...
31 views

### An almost surly fine-time game of coin toss where you win with probability $p$

Given a fair coin and a number $p\in(0,1)$. How do you design a game that finishes in a finite number of tosses with a probability of $1$? And further, with the probability $p$ you win the game. I ...
66 views

### How to find the relationship between an independent variable in a time series and a single dependent variable

I have a dataset of crop yield of a seasonal crop, under environmental conditions (rainfall, humidity, temperature etc.). Daily environmental conditions are recorded over few years with the crop yield ...
56 views

### Find mass matrix in a system of linear equations

Given $z_t=\sum_{i=1}^t \theta_iz_{t-i}+v_t$, where $t=1,...,N$ where $N=1024$. I need to write this in matrix form (a system of linear equations) as $\mathsf{A}\mathsf{z} = \mathsf{z} - \mathsf{v}$. ...
106 views

### How to get free energy surface of a 3d Ising Spin system using Monte Carlo simulation?

I am doing a Monte Carlo Simulation of the properties of a 3D Ising Spin system. I want to get the free energy surface of the spin system from the simulation. It is a magnetization vs free energy ...
102 views

### Finding derivative of Matrix at different grid points using Finite difference methods/ Cholesky Factorization

I want to code this problem in MATLAB. It would be a huge help if someone can suggest to me how I can approach it. I need to solve the below-highlighted equation, I need ...
38 views

### FORM by NIKHEF: unexpected behavior wrt summation

I have two almost identical FORM (by NIKHEF) scripts here: script_1 script_2 which differ only in summation at the end. In first case the summation in done in one step, in the second case ...
21 views

### Plot sinewave on ZX axis [duplicate]

I am trying to plot a sinewave with a bit of 3d perspective along the ZX axis instead of the XY axis. I have so far been unable to get anything that works, and have been unable to locate any examples....
51 views

### Integrate using Composite Simpson's rule

In a question, we have been given the speed of a car at time t= 0,2,4,6,.......,20 minutes.But it asks us to approximate the distance travelled by the car in 30 minutes using Composite Simpson's rule. ...
295 views

### Recursive Algorithm to Calculate Determinant via Expansion of Minors in C#

I have been recently trying to attempt to write an algorithm in C# that would calculate the determinant of a matrix via recursion using the expansion of minors method. I understand that there are ...
66 views

### Simulating magnetic particles in a field free point generated by two opposing magnets

This is probably a long shot with such a short time, but I've been trying to get theoretical data for a project I'm working on. The project involves using a very simplified version of magnetic ...
353 views

221 views

### $LU$ factorization

Our task is to implement a factorization routine that given A in a suitably efficient data structure returns the factors $L$ and $U$ where $L$ is unit lower triangular and $U$ is upper triangular. In ...
952 views

### Gaussian and external basis set. How to write the input correctly [closed]

I have to use the LANL2DZpd basis set. It can be obtained from EMSL Basis Set Exchange. But trying to calculate simple Me2Se molecule : ...
616 views

### Dirichlet boundary condition

I am trying to solve ODEs in matlab using ode15s. Instead of specifying ODEs in the format M * dC/dt = f(C,t) where C is a function of x and t. I want ...
109 views

### solving a non-linear equation with integrals involved

I would like to solve the following equation, wrt $n(e)$ $$f(n(e))=g(n(e)) + \int_{\alpha}^{e} w(n(x))dx$$ The integral there it confuses me. Any suggestion on how I can implement this on a the ...
849 views

### Any note on Immersed boundary finite difference method?

For parts of a talk, I need a note on "Immersed boundary finite difference method", mainly about the reason of appearing this branch in the finite difference methods, considering mathematical ...
5k views

### Confusion Over Navier-Stokes, RANS and URANS in a Flow With Laminar-Turbulent Transition [closed]

I have been working on a transient simulation, using the SST k-w turbulence model in Fluent(TM). An unsteady boundary condition is used: at the beginning of the simulation the flow is laminar and ...
125 views

### Numerically solving differential equations, the domain is very long, [0, +10^6), so the calculating time is very long

Is there any method to deal with this problem? I am using Mathematica to solve the differential equations, but the calculating time is so long because of the large domain $x\in[0,10^{6})$. In fact I ...
862 views

### Understanding and implementing the Fast Fourier Transform

I need to write the fast fourier transform in C++ and I am referring to this formula from wikipedia: But for some reason I am not getting the correct output when I simply enter (1,1) (1,1) (1,1) (1,...
1k views

### explain the difference between 1D Poisson solvers

I compared 2 methods for 1 dimensional Poisson equation solution. One is finite-difference method, "Successive Overrelaxation" from http://www.cs.berkeley.edu/~demmel/cs267/lecture24/lecture24.html; ...
3k views

### How do you install a binary R package?

I need instructions on how to install a binary package in R.
85 views

### numerical solution for differential equation

I have these 3 equations and i want to solve them with numerical methods. so I am using scipy library but I don't know how to solve 3 equations together. R, g, sigma and density are constants. \begin{...
753 views

### Solving Schrodinger equation numerically

Here is the Schrodinger equation that is to be solved: A 1D hard wall potential in $[0, 1]$. The potential within the potential well is given by a linear combination of Gaussian dips v(x) = - \...
76 views

### R language - how to list variables in use [closed]

How can I generate a list of all the variables that have been assigned in an R language session?
42 views

### Solving differential equation by setting vectorization on in MATLAB

This is a follow up to my previous question posted here. I've set up an ode system in MATLAB and I'm trying to vectorize the code to increase the speed of computation. The follow is the code for my ...
135 views

### Ways to solve numerically differential equations in C [closed]

I have to solve numerically a differential equation in C. The equation is: How can I write some code to solve it? Are there some numerical methods (Runge-Kutta maybe?) to solve it? A colleague ...
305 views

### Multi-objective optimization problem - Euclidean space

I am looking for some clues for an optimization problem. My problem consists of arriving to a image by optimizing multiple layers with the pixel position probability. This is an overview of the ...
62 views

### How to get 10 in computer science, using the number 4 exactly four times, and two signs exactly and two operation + exactly? [closed]

How to get 10 in computer science, using the number 4 exactly four times, and two signs exactly and two operation + exactly ?
73 views

### Forward Euler Adaptive Step Size Stability

Given with a generalization using adaptive times-stepping as then is it still reasonable to assume that to ensure stability of the Euler’s forward method we need the growth factor for all n to be ...
90 views

### How to : numerical integration by quadrature in C language / remove NaN

What I wanna solve it the problem following ( by quadrature method ) I want to get two arrays of data ( z & tau ) from z[0], tau[0] to z[2249], tau[2249]. Since the integrand diverges at z=0.9, ...