Questions tagged [precision-and-accuracy]
The precision-and-accuracy tag has no usage guidance.
2
votes
1answer
389 views
Why does the PoissonDistribution not plot around its mean for moderate large numbers?
I plotted the Poisson Distribution for various mean values (plot label and vertical line). The plots does not peak around the mean as the mean increase. Any advice to get the right plot, or at least ...
1
vote
0answers
43 views
NDSove vs ParametricNDSolve
ParametricNDSolve is very practical when one has to execute NDSolve again and again. However is it equally accurate? I have not ...
1
vote
2answers
143 views
NMaximize not always returning solution
This question is related to a previous question and answer here:
NMinimize or NMaximize for a dynamic problem
but tackles a different problem.
I am trying to solve a simple linear quadratic ...
0
votes
0answers
58 views
Numerical calculation Mathematica 11.2 / 11.3 / 12 [duplicate]
Please
I do not understand why Mathematica 11.2 version evaluates numerically the value below
Exp[-800]//N
(* 3.667874584178*10^-348 *)
while 11.3 and 12 ...
1
vote
1answer
98 views
How to make these operations occur faster?
How can I get this section of the code to solve this integration faster. I have rather large values but I don't need it to be too specific. However if I lower the precision it says the integration is ...
0
votes
0answers
36 views
0
votes
2answers
48 views
Precision, accuracy and very large/small exponents with Reduce
Numerical precision/accuracy question here.
I am currently working on solving nonlinear equations with Reduce. Oftentimes, ...
0
votes
0answers
24 views
NumberForm giving incorrect result [duplicate]
The definition of the NumberForm function is the following:
"NumberForm[expr,n]
prints with approximate real numbers in expr given to n-digit precision."
However ...
3
votes
2answers
72 views
Solution to eigenvalue BVP using NDEigensystem to high precision
I'm trying to solve linear (non-self-adjoint) boundary-value problems to as high precision as possible (optimally 1e-15). For example, the below code solves for the first 5 eigenvalues of the harmonic ...
1
vote
0answers
24 views
Getting values of EllipticK with arguments that are very near 1
I need to evaluate EllipticK[m] very close to 1. However, when I get too close to 1 the function defaults to the exact solution for 1 , which is ...
1
vote
0answers
57 views
Confusion matrix using data from two matrices
I have a problem. Any help will be appreciated.
In order to calculate the accuracy, sensitivity, sensibility and F1 score between diseases and their symptoms, I have two matrices with a different ...
4
votes
2answers
130 views
How can I get high precision circle drawing in Graphics, across ten orders of magnitude
I need to visualize some fractal circle arrangements where tangent circles can vary by ten orders of magnitude. In such cases the circles are not being drawn as tangent.
Example: The red and blue ...
0
votes
0answers
45 views
Why doesn't SetPrecision give me the precision I ask for? [duplicate]
I'm dealing with a problem requires a precision of 50 digitals after the decimal point. However, I got the following value when doing so:
I don't know what's going on here, ain't it 0.09 with other ...
1
vote
1answer
68 views
Efficient Round edition with different rounding direction
As pointed out in this post, Mathematica has a special version of Round that
Round rounds numbers of the form x.5 toward the nearest even integer.
A comment by ...
2
votes
1answer
111 views
How to prevent Mathematica from giving inexact answers
Upon doing a simple subtraction 13.725 - 13.5 both Mathematica 11.3 and 12.0 beta version are giving me 0.22499999999999964 ...
3
votes
1answer
177 views
3
votes
0answers
61 views
Slight loss of precision when parsing JSON
Exporting to JSON is working well for me under 11.3. The issue present in previous versions seem to be solved:
...
4
votes
2answers
394 views
Using LinearSolve instead of Inverse does not give a good enough precision
If I want to calculate $B^{-1}A$, then instead of using Inverse, I should in theory just be able to use LinearSolve[B,A].
Now ...
0
votes
1answer
52 views
ContourPlot fails in a simple equation
I'm very new with Mathematica, and I'm struggling with a very simple problem.
I want to plot this
...
0
votes
1answer
60 views
ContourPlot showing breaks in contours
I'm trying find graphically the solutions of the intersection of the following functions.
...
2
votes
2answers
112 views
Why is 0 vs 0.0 causing a precision problem?
I wasn't sure what to title this Question.
I tried calculating different forms of a continued fraction, and I found that I get a correct result when I set d to 0 but a wrong result (in the final two ...
5
votes
0answers
50 views
Small positive machine number calculation in Mathematica 11.3
In Mathematica version < 11.3, any positive Machine‐Precision Numbers exceeding the range [$MinMachineNumber,$MaxMachineNumber...
8
votes
7answers
1k views
How to display very small numbers in Mathematica?
I am trying to evaluate the function:
$$f(x) = \cos(x) - \mathrm{e}^{-2.7 x}$$
at $x = 1.7 \times 10^{-25}$
and Mathematica keeps returning '0.'
How do I evaluate the expression in a better way?
3
votes
1answer
94 views
Problem with the Inverse CDF of Non-central F Ratio Distribution
In[3]:= n = 5; n1 = 4; n2 = 6; γ = 0.05; α = 1/370;
InverseCDF[NoncentralFRatioDistribution[1, n1 - 1, n1/γ^2],
1 - α - (n - n1)/n2]
During evaluation of In[3]...
6
votes
2answers
181 views
Catastrophic loss of accuracy in Orthogonalize
Context
In connection to this question
I am interested in orthogonalizing known matrices.
As a test case, let us consider the definite positive $15 \times 15$ matrix ...
0
votes
1answer
93 views
Good practice about numerical precision
In one of my calculations, I get -1.11022*10^-16 as one of my eigenvalues for a matrix. It's essentially zero and I suppose I could use SetPrecision to make it zero but I wonder what's a good practice ...
0
votes
1answer
60 views
Increasing MaxExtraPrecision arbitrarily changes numerical result
I am trying to confirm that a function $f$ satisfies a particular differential equation of the type $D f=0$, for some differential operator $D$. I set $Df$ as Diffeq...
0
votes
0answers
34 views
Return the precision of the first non zero digit in a number for measurement error representation function
I'd like to return the precision of the first non zero digit in a number. The motivation is so that I can quickly construct my error notation which is the bracketed notation, e.g.
$x = 1.234$ with ...
1
vote
2answers
131 views
How to avoid this type of change of digits in computed numbers?
Is there a way to avoid the digits being changed?
...
0
votes
1answer
38 views
Inaccuracy in Plot3D
This problem might be well-known - in this case, I would appreciate a link, because I could not find anything. My problem: A certain function (super long and nasty expression) needs to be plotted. ...
6
votes
1answer
92 views
Loss of accuracy in orthogonalisation of polynomials using Orthogonalize
Context
As a mean to understand the growth of structure in the universe,
I am interested in characterising the curvature of random fields such as this one:
For this purpose I start with a PDF of the ...
0
votes
0answers
40 views
1
vote
0answers
39 views
DensityPlot, ScalingFunctions, and small values
Edit: I figured out I can use Rescale to retrieve the plot as well as get the correct plot legend. I still can't figure out how to rescale the axes from 10^-9 to 1 ...
1
vote
2answers
91 views
Truncate a number in mathematica
I want to truncate a simple number to n decimal digits. For example, 2/3. I used
f[x_, n_] := N[IntegerPart[x 10^n]/10^n]
but I get
...
1
vote
1answer
49 views
0
votes
1answer
49 views
How to get the correct result in a simple operation in Mathematica
I have the following values for x[[i]], y[[i]] and A[[i,j]]:
...
0
votes
0answers
31 views
Speed and precision with Inverse Laplace transform
I have a problem with an inverse Laplace transform that to me looks like a precision problem when computing with large/small numbers. Scientific background: I would like to compute how photons from a ...
1
vote
1answer
53 views
Performing a FindRoot from Numerical integration
I am trying to evaluate:
FindRoot[Xfnew[γ, w, Hi, mx]*92*10^23*γ^(4/(1 + w)) == 1198/10000, {Hi, hs},
MaxIterations -> 10000]
for some starting value hs,...
0
votes
3answers
32 views
Low precision from function returning matrix
Got a function depending on single parameter "t" defined below which
returns a 2 by 2 matrix
...
0
votes
2answers
78 views
How to deal with the loss of significant digits in this expression with Fresnel integrals?
I needed to solve this integral:
$$\int_1^\infty \frac{dx}{\sqrt{x}} \cos \left(a x-\frac{\pi}{4} \right) \cos \left(b x-\frac{\pi}{4} \right) \cos \left(c x-\frac{\pi}{4} \right)$$
Coming from ...
2
votes
2answers
88 views
What's the smallest positive real allowed in mathematica?
This question may be a bit strange, but in this question, one of the answers suggests substituting some negatives values in a matrix by the smallest positive real number allowed. So, I was wondering ...
0
votes
1answer
41 views
Simple division with high precision in Mathematica [closed]
I want to do a simple division i.e. 0.70524/0.51824 . What I want is to find the result of the roundation of this division for precision from 1 to 19 decimal digits....
2
votes
1answer
75 views
Inaccurate zero eigenvalues for 7*7 matrix [closed]
I have symbolic entries for all the elements of a 7*7 matrix. At the symbolic level Eigenvalues gives two zeroes and five others that are extremely complicated. At ...
3
votes
1answer
56 views
Numerical precision problem
I have this simple code:
ep = 1 - 80000000000 (-(199999/200000) + 1/E^(1/200000))
ep // N
-8.27404*10^-8
...
0
votes
0answers
39 views
Solving a system of linear equations in Mathematica regarding the errors of different methods
I have a system of equations, i.e.
0.62243x + 0.51824y = 0.70524
0.71497x + 0.59496y = 0.80996
I have 3 ways to solve this system (there are more but I am ...
0
votes
1answer
80 views
Problem with solving differential equation using NDSolve
I am trying to solve differential equations subject to condition z[0] == 0 and z[tmax] == 10 Pi.
...
0
votes
2answers
61 views
Formatting a list of values and dependent formatting of corresponding errors list
I am making a table of data that I wish to output using TeXForm.
Rather than manipulate the values in LaTeX (e.g. using the ...
