Questions tagged [precision-and-accuracy]
The precision-and-accuracy tag has no usage guidance.
1
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0answers
22 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 ...
0
votes
0answers
20 views
Confusion matrics to estimate the accurancy of classification using Diseases associated to their symptoms [closed]
Hi guys does anybody have a suggestion to create a logarithm for the confusion matrices , the propose for this confusion is to estimate the accuracy of ranked model as you see in title I have matrics ...
1
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0answers
42 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
121 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
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0answers
39 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
66 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
102 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
163 views
3
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0answers
56 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
374 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
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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
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1answer
58 views
ContourPlot showing breaks in contours
I'm trying find graphically the solutions of the intersection of the following functions.
...
2
votes
2answers
103 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
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0answers
47 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
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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
90 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
178 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
67 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
57 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
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0answers
33 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
129 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
37 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
89 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
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0answers
39 views
0
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0answers
31 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
62 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
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1answer
48 views
0
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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
30 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
52 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
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2answers
73 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
87 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
69 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
53 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
79 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
1answer
46 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 ...
3
votes
1answer
64 views
0
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2answers
66 views
equal expressions give different numerical result
I have two expressions, and they are really equal:
...
2
votes
1answer
146 views
NIntegrate fails to converge
I am trying to compute this integral for different a with 0.0001<a<0.5,
...
7
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1answer
237 views
How does Mathematica determine when to use scientific notation?
I have code that takes an initial guess for a set of parameters to use in a function that I want to minimize, calculates the function, prints the value, recalculates new parameters via the gradient ...
7
votes
3answers
122 views
How to create an Interval object with specific end points?
When creating an Interval object, the end points are automatically widened when an end point is an inexact number. For instance:
...
14
votes
4answers
323 views
Terrible accuracy of DawsonF
DawsonF[30.] returns 0. The correct value is 0.016676...
At least it prints a warning message,
...
1
vote
2answers
44 views
Diagnosing the numerical stability of a function
I have programmed a function f[x] that seems to be very unstable numerically. More precisely, I noticed that for certain arguments in arbitrary precision, the ...
