Questions tagged [numerical-value]

Question relating numerical representations, operations and methods, including approximate results instead of exact symbolic results.

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2answers
70 views

equal expressions give different numerical result

I have two expressions, and they are really equal: ...
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0answers
23 views

Raising a negative number to a fractional power, why the result is different? [duplicate]

In the math theory, we know have $$(x)^{\frac{m}{n}=}\sqrt[n]{x^m} \ ,$$ it means $$(-1.5)^{\frac{1}{0.3}}=(-1.5)^{\frac{10}{3}}=\sqrt[3]{(-1.5)^{10}}=\sqrt[3]{1.5^{10}}\simeq 3.8634 \ .$$ But in ...
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0answers
171 views

On Ж, and the fine-structure constant

I'm trying to reproduce the results from a certain infamous paper that has been moving around the web for the last few days. The details are irrelevant. This paper claims to have a closed-form ...
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2answers
114 views

Product of large number with a very small number returns zero because Mathematica sets the very small number equal to zero [closed]

I have a product Exp[-I*Pi*x]*BesselK[-1, 2.43*Ix]. Now, Exp[-I*Pi*x] grows larger and larger as $x$ increases for imaginary ...
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0answers
51 views

What is the acceptable error in numerical calculations? [closed]

I am doing a calculation where I try to simplify a very complicated complex function. I did this step by step and I checked that the numerical values that the function gets for certain values of the ...
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1answer
86 views

Taylor Series of numerical solution of FindRoot

I have found the inverse to the following equation by using FindRoot. I want to have a Taylor approximation (say starting from ...
6
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4answers
128 views

Suppress trailing 0s in numerical values

For example, this is what I want In[1]:= N[Table[4^(i/4), {i, 1, 4}]] Out[1]= {1.41421, 2., 2.82843, 4.} But if I want a few more digits only from the irrational ...
3
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0answers
47 views

Is there a function that returns me the largest common divisor? [closed]

Is there a function that returns me the largest common divisor? I tried this: Intersection[Divisors[200], Divisors[280]] // Last
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1answer
118 views

How to test if a solution of NDSolve is positive

I want to solve a differential equation numerically and determine one of the parameters in the D.E. The goal is to determine $M$ such that the function goes asymptotically to zero or to put it in a ...
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2answers
115 views

Computing a sum with high precision

I am aware that a similar question has been asked, for example, here and here, but none of the proposed solutions solves my problem, so please wait before you mark this question as a duplicate. ...
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1answer
76 views

How do I to remove a factor of 1 [duplicate]

I evaluated Subscript[ε, 1, 2] = 0.5 Subscript[γ, 1, 2] 2 μ Subscript[ε, 1, 2] 1. μ Subscript[γ, 1, 2] How do I to remove ...
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1answer
66 views

How to make Mathematica show small and large results? [closed]

I have two equations with x=r+Log[-1+r] and v=(1-1/r)/r^3 forms. When I substitute ...
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0answers
39 views

Getting the coordinates of a specific point out of a plot [closed]

I have the following piece of code that in the first part calculates and plots a function and it uses it in the second part to perform an NDSolve. After that I am plotting two functions. What I would ...
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1answer
131 views

How to avoid rounding error, when exporting numerical values

How to avoid the rounding error, when exporting data like this: ra = Range[0.004, 0.074, 0.0005]; Export["range.txt", ra] The result is this:
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0answers
98 views

How solve this equation and plot the results?

I want to solve the following function and get values for $\omega$. $$\omega - \omega_{21} + i/\tau_{2} - s_{1}\alpha_{1}(\omega)[1+f(\omega)] = 0$$ The function $f(\omega)$ is the troublesome ...
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1answer
44 views

Numerical solution to integration of function which parameters define the integral limits

I have following equation: $\int^{\delta_c}_{\delta_c-\pi}\sqrt{h^2_c(\cos(\delta_c)^2-\cos(\delta)^2+\Omega_c(\delta_c-\delta)}\text{d}\delta=\pi$, where $\delta_c=\frac{1}{2}\arcsin\left(\frac{\...
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1answer
86 views

Numerical artifacts appearing ONLY on boundary of 3Dplots and not on Plot

I have a behavior with 3D plots I really don't understand and I would like to correct it. I have a 2D function to plot, here is its graph with Plot3D : We can see that on the top boundary of $\Delta ...
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1answer
101 views

How see 0 instead of (0.*10^-4)? [closed]

I have this: ...
11
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3answers
1k views

Solve Laplace equation in Cylindrical - Polar Coordinates

Hey mathematica stackexchange!! I've got a (possibly stupid) problem. I've tried many things to no avail, and I've read every post I've found on Laplace's equation. Background: I'm trying to find the ...
3
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1answer
143 views

How to make Mathematica substitute exact numerical values of (derivatives) 2F1

I have a long output that contains Taylor expansion of some function. Some of the coefficients are combinations of the (derivatives of) 2F1 at nice integer values of the coefficients. I can see that ...
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1answer
86 views

Numerical error in compile, Strange behaviour in numerical evaluation

First of all, apologies for the large numbers, I couldn't find a working example for a far lower order and the zeros are necessary... my problem is this: I have a large polynomial (from high-order ...
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1answer
56 views

Partial Derivatives of numbers not evaluating?

I have code of the form someFunction[xx_?VectorQ] := 1 + anotherFunction[xx] myfunction[xx_?VectorQ]:= Sum[D[someFunction,xx[[a]]],{a,1,4}] After this evaluates, ...
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0answers
55 views

How to convert a dollar fraction into a normal dollar amount

I'm trying to use Mathematica to compute compounded interest. I used Wolfram Alpha, and it gave me the code ...
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1answer
75 views

Function not evaluating to zero - numerical errors

I have a complex but analytical expression that should always evaluate to zero for certain values, but I'm getting strange numerical noise I think I can avoid. The problem seems to occur in a ...
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1answer
33 views

Setting the parameters in a defined function vs replacement rule in the formula

I have the following definition in my Mathematica notebook. ...
2
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1answer
39 views

Question related to IntegerPart

I am having trouble understanding the following result: Through[{IntegerPart,FractionalPart}[{100 4.02}]] {{401}, {1.}} ...
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0answers
59 views

Integrate a multivariate function similar to a delta function

I am doing a code in Mathematica. I have the following function: ...
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0answers
82 views

Change of variables in integral is not working

Consider the matrix ...
3
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1answer
89 views

Is this bifurcation or numerical error?

I encountered a definite integral (with parameter $k$) that produces the "chaotic" figures below. $$F(k) \equiv \int_{\theta_k}^{\theta_{k+1}} f(\theta, J \sin\theta - k)\,\mathrm{d}\theta~, \qquad f(...
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1answer
78 views

Numeric values for MinkowskiQuestionMark

Why NumericQ[MinkowskiQuestionMark[Pi]] returns False? Is it defined only for algebraics? Numerical evaluation gives some number,...
2
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2answers
93 views

How to avoid problems with the large imaginary part of LegendreQ?

I am trying to evaluate sums involving LegendreQ[n,x], the n-th order Legendre function of the second kind $Q_n(x)$, at large $x>1$. However, the problem is that ...
2
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1answer
113 views

How to get Mathematica to Return an Actual Numerical Result For Probability? [closed]

This is a painfully basic question. It's probably been answered before (or might be in one of the documentation packages), but I've been looking for some time and can't find it! (Though it could very ...
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1answer
92 views

Strange numerical values [closed]

I have a table of numerical values which contains a lot of strange values. ...
0
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2answers
112 views

Why does mathematica not recognize the equality of these two terms? [closed]

I have two expressions which I have analytically verified to be equivalent but when I check them numerically via mathematica I don't obtain numerical agreement. They are ...
8
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2answers
254 views

how to get single, and quad Precision out of Mathematica which match Fortran result

by default, if a number has decimal . after it, then Mathematica will do computation using machine Precision, which on my PC (intel hardware) running windows 7 64 ...
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2answers
78 views

Numerical Function

I want to animate a Point moving on an ellipse, but the angle I need to use is a numerical solution from an epression. How can I get mathematica to just take the value from the animated nummerical ...
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1answer
51 views

TrigExpand for numerical multiples of angles

After some calculations, Mathematica gives me a result which has in it a term Cos[2.x] (I cannot skip numerical computing, that's the reason for the ...
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0answers
40 views

Error caused by ThreeJSymbol

I do not understand what causes non-physical answer in my code although I have read about the error. I am also getting the following error, how could I fix the example error: "CompiledFunction::cfte:...
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1answer
44 views

Numerical Results with replacement rules [duplicate]

Why are the following outputs different? N[(x^2 + y^2) /. Thread[{x, y} -> {1., 1.}], 10] gives 2.. N[(1^2 + 1^2), 10] ...
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1answer
102 views

Get Finer Grid with respect to x using NDSolve in Mathematica

I use Mathematica NDSolve to numerically solve V(x,t) and export the numerical values of V(x,t) at each x and t into an external csv file. I find Mathematica only numerically give results with step ...
5
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0answers
258 views

How does NSolve find the roots to an equation?

I'm using NSolve to find the roots to a transcendental equation. For this, I need to specify a bounded region where roots are searched. What I want to know is how <...
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1answer
66 views

Optimising matrix calculation [closed]

I was calculating the elements of a matrix like this: ...
18
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2answers
710 views

Error and uncertainty propagation: Is using Precision/Accuracy a sound strategy?

Questions What are the available resources to deal with experimental error and uncertainty propagation in Mathematica? Given that Mathematica already uses linearized model of error propagation on ...
2
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1answer
165 views

Orthogonalize with a custom inner product

Bug introduced in 9.0 or earlier and fixed in 10.0 I was trying to define a custom inner product function for Orthogonalize, and have been getting some odd behaviour. Here's a MWE: I try to compute ...
0
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0answers
60 views

Evaluating expression with machine arithmetic gives wrong answer but evaluating with arbitrary precision works

I need to understand how Mathematica approximates symbolic numbers. I have an awful symbolic number to compute. When I do N[variable] Mathematica gives me <...
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0answers
136 views

Limit of a List

Is it possible to take the limit of a list instead of using the Limit method? I'll try to explain what I mean. I am generating a list of numbers that converge to some number. The generated numbers ...
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0answers
82 views

Why the data from Do-command disagree with the plot I get using them? [closed]

This is a question relevant to How to plot output data of Do-command? The Differential Equation at hand now is $\frac{d^2 f}{dx^2} + \frac{2}{x+0.1} \frac{df}{dx} = k(f)$ I give the code with the ...
5
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3answers
234 views

How to plot output data of Do-command?

The following in a simple numerical solution of the simple harmonic oscillator. ...
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0answers
111 views

Problem with FindRoot + NDSolve + InterpolatingFunctionDomain

I'm trying to find the root (po) of a complicated problem (where s is a parameter): First, I need to define some functions, which involve numerically solving a differential equation. ...
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4answers
230 views

How to solve the following set of equations to find values of a1, a2, and a3

i am new to Mathematica, Can some one kind enough to show me how to solve the following set of nonlinear equations to find a1, a2, and a3.. ...