Questions tagged [precision-and-accuracy]
The precision-and-accuracy tag has no usage guidance.
560
questions
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13 views
Why increasing PrecisionGoal and WorkingPrecision is deteriorating my results
I am minimizing a variable subject to many very complicated constraints, like
...
0
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0answers
22 views
General::munfl - Precision lost in LinearModelFit
I am new to mathematica so I am confused regarding the loss of precision in LinearModelFit. In building a linear model with uora (1 or 2) and encodeSeverity (1,2 or 3)
...
3
votes
0answers
52 views
How to deal with too small numbers
When dealing with a code that produces too small numbers (in a complicated way) like
0.33691 4.015757066049965*10^-330
I get the following warning
General::munfl: ...
5
votes
1answer
117 views
Accurately computing $\sum_{j=2}^\infty \frac{(-x)^j}{j!} \zeta(j)$
I'm doing a sanity check of the following equation:
$$\sum_{j=2}^\infty \frac{(-x)^j}{j!}\zeta(j) \approx x(\log x + 2 \gamma -1)$$
Naive comparison of the two shows a bad match but I suspect one of ...
0
votes
0answers
31 views
Solving a determinant to get non-zero roots in a heat transfer problem
I am trying to solve a mathematical model of a heat transfer problem.
As an intermediate step there is a characteristic equation in the form of a determinant, which needs to be solved for variable <...
0
votes
0answers
39 views
How do I increase an amount of digits after the point?
I have an expression such as:
Log[0.784637, 517.8796]*ArcTan[-1.112673]*0.4256^(-2.034)*Sqrt[3.567]
and I get 3 digits precision. I tried:
...
2
votes
1answer
43 views
N::meprec warning when setting precision
How come
N[ Log[ Cos[1]^2 + Sin[1]^2 ] ]
evaluates to 0. without any trouble, while
...
5
votes
1answer
181 views
Airy function zeros, conflict (error?) between Wolfram Functions vs. Mathematica
According to functions.wolfram.com, the zeros of the Airy function $\operatorname{Ai}(z)$ occur at $z_k=f\left(\tfrac{3\pi}{8}(4k-1)\right)$ for $k\in \mathbb{N}$ where
$f(d)=-d^{2/3} \left(1 + \frac{...
1
vote
2answers
37 views
Compile generates non-tensor object warning for this simple function
Compile generates the following error (CompiledFunction::cflist: Nontensor object generated; proceeding with uncompiled evaluation.) upon execution of this simple ...
2
votes
1answer
93 views
NIntegrate fails to solve a double oscillatory integral
I need to compute the following integral:
...
1
vote
1answer
64 views
Removing artifact in Plot[1-(1-x)^Floor[2/x],{x,0,1/20}]
The input
Plot[1-(1-x)^Floor[2/x],{x,0,1/20}]
yields
where the white space we see below the curve near $x=0.01$ is an artifact. How can we fix this simply? ...
1
vote
0answers
39 views
Why does this reduce evaluate with exact numbers but not numbers specified to 20/50/200 decimals of precision?
Consider the following lines of code:
...
1
vote
2answers
70 views
Function decomposition to Fourier series using first impulse function
I have periodic function with certain first impulse function and period value. My task is to decompose it to approximate Fourier series (k_max = 10) using Laplace transform of first impulse function:
...
1
vote
0answers
48 views
Why don't AccountingForm, NumberForm and DecimalForm print more decimals?
I have the following set of equations:
...
0
votes
0answers
14 views
Setting precision of a result for the next calculation
Sorry for my easy question.
I would like to learn how I could change the precision of a value to use it for the next calculation ?
Lets say, a=9.96329x10^-13, in fact this value is so small and can be ...
0
votes
2answers
46 views
Confused by results of a simple computation [duplicate]
If I define
f[x_] := (1 - Exp[-2 x^2])/(x Sin[x])
and then enter
N[f[10^-5] - 2, 100]
I get the result
$$-1....
0
votes
1answer
48 views
The value of the function with a very small Imaginary part but can be Plotted
I have a function Y[x_,β2_], It can be plotted normally. But when I take specific values, I get something like +0.000000*I when ...
4
votes
2answers
176 views
Slider changes Pi to a MachinePrecision number
Problem
Consider the following code:
DynamicModule[{a = {0, Pi}, b = 4},
{Slider[Dynamic@b, {a}], Dynamic@b}
]
I want a Slider...
0
votes
1answer
86 views
Accurate Numerical values of a given functional
Consider the following functional :
$$
I(x,s) =\int_0^\infty\mathrm dy \frac{F(x + \mathrm iy, s) − F(x −\mathrm iy, s)}{\mathrm e^{2πy}-1},
$$
where $ F(z, s) = \dfrac{\sin^2[π\Gamma(z)/(2z)]}{z^s} $....
0
votes
0answers
34 views
How to copy and paste numbers with “`” mark and use them in calculations, without using N or setting precision every time
Suppose we have run a calculation and get a number like
2.758952615889003`
If we then copy-paste this number and do a calculation like
...
2
votes
1answer
22 views
1
vote
2answers
92 views
How do you overcome recursion limits when using DSolve?
I have the following program to solve for the neutron to baryon ratio during BBN. I've replaced many of the derived values with constants in order to focus on the problem:
...
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0answers
45 views
3
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0answers
73 views
0
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2answers
58 views
Precision in Integrals and NDSolve
I have a simplest code for NDSolve, the problem is I am dividing two small numbers, the denominator is so small that it gives me infinity as an answer, how can I increase the precision to get a ...
22
votes
3answers
9k views
5
votes
1answer
87 views
Find the number of correct digits to compare approximation with exact value
A) For simple example suppose i want to approximate $\pi$ using $\frac{22}{7}$ and $\frac{355}{113}$.
...
1
vote
2answers
124 views
Why can't Mathematica express a minus operation between two decimal numbers with several places? [closed]
A example of the problem. This is a print from mathematica with the demonstration of the issue.
3
votes
1answer
47 views
How to set Working Precision/ Accuracy global for the entire notebook in mathematica
F1[r]=((37.3042 - r) (-25.578 + r) (62.8822 + r))/(3000 r)
FindMaximum[F1[r], r]
The output is {0.0345106, {r -> 31.0723}}.
...
1
vote
1answer
46 views
10
votes
1answer
98 views
How to control floating point precision when `Export`ing to obj format?
Suppose we have a MeshRegion that we want to export to an obj file with, say double precision. Is that possible with Export? And ...
0
votes
2answers
38 views
How to export InputForm of a number
I need to export full form of a number i.e. the actual form with which Mathematica works. For example, full form of a number is
...
0
votes
0answers
87 views
Why can't NDSolve(Value) solve Maxwell eq. for plane wave i.c.'s when going to spherical coordinates (it works fine in Cartesian coordinates)
I would like to use NDSolveValue (or NDSOlve) to solve a set of PDEs in spherical coordinates. I started with a simplified example that resembles the problem I actually want to study, but where I know ...
2
votes
2answers
93 views
Most efficient strategy for integrating over removable poles?
I am finding many situations where I have to numerically integrate some function $f(x)$ of the form:
$$f(x)=f_{s}(x)-ax^{-n},$$
where $f_s$ is a special function with a finite-order pole that is ...
2
votes
1answer
81 views
Shouldn't NIntegrate return a number whose Precision is PrecisionGoal, not WorkingPrecision?
I know that Mathematica has great built-in precision tracking, so when you do calculations with arbitrary-precision numbers, Mathematica keeps track of the precision on the result. Given this careful ...
4
votes
3answers
143 views
How to convert a real number to a string only in the original length?
Example: I have this number
num = 2.9525730420542016*10^1798
(* 2.952573042054202*10^1798 *)
If I want to convert it to a string, I don't get "2....
3
votes
1answer
46 views
Rationalizing only specific terms in an expression
How can I change an expression like
A = (-1. a)/(x + y) - (2.1 b)/(x + y) + 4.1 + 2. x + (3. r s)/(x + y)
so that -1. a becomes ...
2
votes
1answer
64 views
Problem with the precision
I am trying to plot eigenvalues of a matrix.
I get some errors like “precision may be lost”.
As a result, there are some unwanted jumps in the plot.
Any suggestion of what am I doing wrong?
Thanks
1
vote
2answers
65 views
Accuracy of Mod[x, 1] and FractionalPart[x]
The difference between exact and numerical computation is clear to me. But why is
...
8
votes
2answers
256 views
Computing separatrix orbit
I would like to numerically compute the separatrix orbit for a particle in a few potential wells, given by the negative of
...
0
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0answers
35 views
How to avoid machine underflow for plotting and integrating?
I am trying to integrate the following integrand, which I have plotted:
...
1
vote
1answer
75 views
Lowest Eigenvalue of a large sparse matrix without choking up the RAM (Corrected) [closed]
I am trying to find the lowest eigenvalue of a large sparse matrix of dimension N (=$3^n$, where n is number of particles in system ) using ...
2
votes
4answers
271 views
1
vote
1answer
38 views
Problem with label and precision
I need to define a function that depends on a variable taking values on discrete values, for example:
...
2
votes
1answer
178 views
(Numerical) calculation of nested integrals
The problem
I'd like to (numerically) compute nested integrals of the type $$I(a;k) \equiv \left( \prod_{i=1}^k \int_0^\infty \mathrm{d}x_i \right) \exp \left( - \frac{1}{4a} \sum_{i=1}^k \left( x_i - ...
3
votes
0answers
43 views
Behavior of $MinPrecision seems to have changed between 12.0.0 and 12.1.1
I am running into a very weird bug where setting $MinPrecision to some value (in this case 200) has a very different and ...
1
vote
1answer
92 views
Exported Excel File - decimals
Im trying to export data from the interpolating function result to excel.
everything works fine and the plots are as expected, but if I want to export these data to excel using
...
3
votes
2answers
97 views
Why is DistributeDefinitions taking so long with 100-300 Mb constants?
Why does DistributeDefinitions take so long to distribute variables that are 100-300 Mb in size?
I am setting up ParallelTable ...
0
votes
2answers
146 views
Can someone please comment on the efficiency of Mathematica, Maple and Matlab in conditional plotting?
I use Mathematica to plot
...
1
vote
2answers
67 views
How to make sure that the number of PlotPoints is sufficient for giving the complete result? (How to have a plot of the whole solutions?))
I want to see the domain in which function $f$ is positive. I use this code
...
