Questions on the numerical functions of Mathematica, implementing numerical methods and numerical computing with Mathematica.
2
votes
1answer
79 views
Use Mathematica to determine the falling law
We have a one-variable equation $\rho(R)$ where
ρ = (14656.4+277.526*R^2)/(45.9225+R^2)^{5/2} + 0.370036/(R*(0.25+R)^3)
This equations describes the evolution of ...
0
votes
0answers
46 views
Inversion algorithm for Laplace Domain
I'm trying to invert an equation in the Laplace domain using Stehfest algorithm. It works very fine, but since I'm trying to represent a sinusoidal behavior I need a different algorithm that makes use ...
7
votes
2answers
196 views
Is there any fast way to solve a quadratic matrix equation in Mathematica approximately?
Let the square nonsingular matrix $M$ is a given convergent matrix. What are the best scalar values for $\alpha$ and $\beta$ (in the real numbers domain), at which the following quadratic matrix ...
-1
votes
0answers
68 views
How to Divided by 200% [closed]
I have a question,
The price is $200.50 included tax 400%.
How much the real price without tax?
Is it $244.?
4
votes
1answer
76 views
Strange behavior of Mathematica regarding calculation time
Today I witnessed the following strange behavior of Mathematica, when it comes to calculation time involving larger nested lists. The following is the short example that I setup, I am sure one can ...
5
votes
1answer
93 views
Counting the number of operations performed during a calculation
I need to know how can I count the number of operations performed during a calculation of a CompoundExpression.
In some of these expressions there are ...
3
votes
0answers
97 views
Crank-Nicolson with NDSolve?
As far as I understand, the Crank-Nicolson method (a.k.a. trapezoidal method) can be expressed as a second order implicit Runge-Kutta method. It's Butcher tableau is:
...
9
votes
1answer
92 views
Apply N only outside a certain function
1 + f[1] // N
gives
1. + f[1.]
I don't want the argument of f evaluated by N; I ...
1
vote
1answer
69 views
10
votes
0answers
63 views
Why do NumberForm and Round apparently use different tie-breaking methods?
When rounding numbers (for example, rounding a real number to the nearest integer), the "round to nearest" rule is usually used. For example, 1.4 is rounded down to 1 and 1.6 is rounded up to 2.
...
0
votes
0answers
74 views
How to Output Chi-Squared Statistics when using NonLinearModelFit
I am using NonLinearModelFit for some curve fitting and I was wondering if NLM is able to output chi-squared/leastsquared statistics from the best-fit parameters and confidence intervals. From my ...
0
votes
1answer
49 views
1
vote
1answer
84 views
find derivative with defined function
s[a_, b_] := NDSolve[{y''[x] == y[x] Cos[x + y[x]], y[0] == a, y'[0] == 1}, y, {x,0, b}]
I need to find the minimal of $\int _1^by[x]^2$ in the region ...
-4
votes
1answer
120 views
findroot, derivative in defined functions
I apologize for my unclear question, I will write it in a more detailed way.
I first define:
...
4
votes
2answers
137 views
Numeric calculation of Hessian
I want to calculate the Hessian matrix for a function that can only be evaluated numerically. So far, I have the following (where f is just for testing):
...
