For questions on the use of machine-precision real numbers (also known as floats), the numbers that can be directly manipulated through the underlying numerical capabilities of your computer system.
1
vote
0answers
79 views
Precision of a complex number
In an output I'm getting a number like -0.33998187034939803 + 0.I. Finding ...
1
vote
1answer
167 views
Why is arithmetic faster for inexact arithmetic?
I have been trying to compute eigenvalues of a rather sizable matrix A, about $500 \times 500$ (but sparse). I asked Mathematica to compute ...
2
votes
5answers
411 views
Why is this Mandelbrot set's implementation infeasible: takes a massive amount of time to do? [closed]
The Mandelbrot set is defined by complex numbers such as $z=z^2+c$ where $z_0=0$ for the initial point and $c\in\mathbb C$. The numbers grow very fast in the iteration.
...
5
votes
1answer
167 views
DeleteDuplicates[] does not work as expected on floating point values
Here is my simple example, and in this case function DeleteDuplicates does not work as expected.
I want to FindRoot of my ...
0
votes
0answers
86 views
Issue with WorkingPrecision
I am having the following issue.
I am evaluating a numerical integral, and I need high precision to get good values of the function being integrated.
...
-2
votes
1answer
149 views
Problem with solving a differential equation [closed]
I need to solve the following differential equation:
NDSolve[{R[r, t], R[r, 0] == r/1000}, R, {t, 0, 30}, {r, 1, 30}]
Where ...
0
votes
1answer
146 views
Adding precision for the calculation of a function
I have some function $f(x)$ I wish to evaluate, which is yielding divide-by-zero errors for sufficiently large inputs. How do I increase the precision with which this function is evaluated in order ...
7
votes
2answers
249 views
Precision differences
I run this sum and get the symbolic answer below :
Sum[ (1/(k^2 - k) - 1/k^2), {k, 2, Infinity}]
$2 - \frac{\pi^2}{6}$
I look up the sequence on OEIS and ...
1
vote
1answer
110 views
How to Chop correctly?
I want to count degeneracies in a list called spectrum. The list contains numbers of double (~ 15digits) precision. So it makes no sense if the noise below this ...
2
votes
0answers
115 views
Why to do parentheses change the results of a calculation?
I'm getting results that are sensitive to where I place parentheses with respect to operations that are associative1 (and should thus be insensitive to such placement). For example, if I define2
...
2
votes
2answers
251 views
FindRoot errors
I'm trying to solve a system of two equations in two variables for some range of parameter values. I use ContourPlot to see where I should look for a solutions and ...
2
votes
0answers
192 views
Set Global Maximum Precision
I'm sure this has been asked before, but I've looked around and can't figure it out:
How do I set a global maximum precision for a notebook (or in general, globally)?
I have a large notebook in ...
3
votes
2answers
214 views
Precision of number not maintained when saved via Export
Assume that the output of my calculation is a and is a number such as:
a = 100.1252135246354847;
...
4
votes
1answer
154 views
Could the PrecisionGoal for NDSolve be a negative number?
The help of Mathematica doesn't say so much about the PrecisionGoal for NDSolve, and I never considered much about it even after ...
9
votes
3answers
244 views
Mathematica Plot: Inconsistency when plotting large values
I am working with a function in Mathematica and I am getting some inconsistencies when I plot it. As I really need to understand were this comes from I would appreciate any help.
I am working with a ...
5
votes
1answer
232 views
Infinite expression 1/0. encountered - caused by precision?
Planck's law dependent on frequency rho is as follows:
B[T_, h_, rho_, k_, c_] := (2 h rho^3)/c^2 1/(Exp[h rho/(T k)] - 1)
As you can see, the denominator can ...
7
votes
2answers
316 views
Dr. StrangeNumbers or: How I Learned to Stop Worrying and Love Floating Point Arithmetic
The following is the program.
...
15
votes
1answer
342 views
Quadruple-precision (128 bit) arithmetic
Is it possible to force Mathematica to perform computations with hardware supported quadruple-precision? The following test suggest, that all of the computations with fixed precision, different than ...
7
votes
1answer
105 views
Using Differences on data: trouble with floats and doubles
Consider the following data set (after I have run FullForm), which is imported from a file (stored typically as 10.040):
...
10
votes
4answers
687 views
Numerical underflow for a scaled error function
I calculate scaled error function defined as
f[x_] := Erfc[x]*Exp[x^2]
but it can not calculate f[30000.]. ...
3
votes
4answers
388 views
Mathematica Precision
How can I set the output precision of the following statement to 10 decimal places? I was looking through the documentation, and for some reason, all I could find was ...
7
votes
2answers
197 views
Dealing with numbers too large for machine precision in Graphics
Graphics only supports machine precision numbers (i.e. number that can be converted to machine precision). Take for example
...
19
votes
2answers
471 views
Meaning of backtick in floating-point literal
If I compute, say, 1/3//N, Mathematica displays
0.333333
as the result.
When I copy that output to use elsewhere,
the paste ...
