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2answers
46 views

Chains of approximate numeric equalities

Mathematica considers two numbers equal if "at most their last seven binary digits" differ. For example: ...
0
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1answer
49 views

What does it mean that “there are no significant digits to display”?

So I substitued with the following values in my function T(x,n) and it gave me this red box with the value in the picture. When I hover over it, it tells me that there are no significant digits to ...
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0answers
29 views

data fit using second order PDE

I'm trying to find the parameter for second order PDE using data. i don't know what is the error of that, ...
2
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1answer
50 views

What Heads do not have the attribute NumericFunction, but still give True in NumericQ?

The following expressions give True in the NumericQ test: ...
1
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1answer
63 views

Can't get a numerical value for this vector operation

I have written these codes: ...
1
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0answers
49 views

Vinculated boundary conditions [closed]

I have a problem in the form: $-y''(x)+V(x)y(x)=0 $ with the initial conditions: $\quad y'(0)=k \ y(0), \quad k=cte$ The $V(x)$ is a model's parameter, for example $V(x)=\frac{6}{\left(x+2\right)^...
1
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0answers
37 views

Why doesn't N[0.33333, 3] return 0.333? [duplicate]

Basic question, other answers I found didn't really seem to address this. N[x,3] seems to only work if x is analytic instead of ...
0
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2answers
91 views

I'm trying to solve a system of complex equations

I'm simply trying to solve a system of equations and mathematica can't do it for all values over the region of interest. I have a 3x3 matrix that has a specific parametrization and after squaring the ...
3
votes
3answers
94 views

How to change random values in manipulate?

I made a Manipulate box that is working very well, using lots of random numbers. I would like to add a button to "reset" (i.e. to change, randomize, or reselect) all the random parameters. Here's ...
10
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2answers
272 views

What is the fastest way to compute digits of $\pi$ using Mathematica?

There are a lot of ways to calculate digits of $\pi$ using Mathematica. The most naïve way I can think of is N[π, 100000000] Of course, there are a lot of fast ...
3
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2answers
89 views

Role of Accuracy in numerical evaluations, SplitBy vs GatherBy

This is a follow-up question to this question. I generated a list by substituting the results of a solve[] routine and set: ...
0
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0answers
46 views

How to get x = 1.234 from {x -> 1.234}? [duplicate]

I'm a complete beginner in Mathematica (started a couple of days ago). I've solved a function using "Solve" and the result is this one: Out[1] = {x -> 0.000942939} How do I get the 0.000942939 ...
4
votes
1answer
178 views

Recognize physical constants?

Is there some way to ask Mathematica to recognize physical constants, such as 32 or 9.81 (gravitational acceleration, in different units, at Earth's surface)? I have in mind something like the "...
1
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0answers
66 views

Using Classifier with NearestNeighbors methods

I am using a Machine learning toolbox on mathematica. I have 8 classes. Training data: for each class, there 100 samples with size 160. I used this code. ...
0
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0answers
41 views

Maintaining working precision in my program

I am badly stuck with this program I am writing. I want output of program below to be precise up to 25 digits after decimal point. I am supplying all inputs with precision 25. But after each iteration ...
0
votes
1answer
54 views

How to calculate digits of Trott Constants?

How to calculate digits of numbers (Trott Constant) whose continued fraction representation is the same as the digits of its radix representation with Mathematica?
0
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0answers
34 views

Handling a matrix with components greater than machine precision

I have four quantities stemming from a 4th order differential equation. I can represent these as a vector which is a product of a 4X4 matrix $$ M=\left\{v,\frac{\partial v}{\partial x},\frac{\partial ...
4
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2answers
127 views

Torus-geometry algebraic equations using Nsolve and Reduce

Somehow a set of naive-looking equations cannot be solved by using NSolve. Mathematica returns a message like this: ...
1
vote
1answer
129 views

How to find and express all polynomial roots with greatest precision?

I've already plowed through the documentation and a bunch of other Questions on this, but I've only found partial or tangentially related answers. I need numerical results for all of the complex ...
0
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2answers
134 views

How to make an Histogram where the data are strings? [duplicate]

Histogram[{3, 3, 2, 2, 2, 2, 2, 1, 1}] works great to give you an histogram in which mathematica counts the occurence of each number and makes the plot. Is there a ...
1
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0answers
47 views

Combining Manipulate and NDEigenvalues [closed]

I think there may be a quick solution to this problem which I can't seem to fix at the moment. The question is how do we eliminate the error in the following ...
2
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1answer
48 views

Non-integral common denominator

I have a list r = {114.49, 311.876, 538.704} whose elements are multiples of a non-integer value. I want to find the common denominator ...
2
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0answers
41 views

Differences in AbsoluteTiming for similar codes

Consider the two following codes with the same SeedRandom (which ensures the same set of random numbers) but different use of the ...
1
vote
2answers
174 views

How to solve this two algebraic equation simultaneously for u and H ?(all real number)

I want to find the non-zero value of H when beta is changing(especially what value of beta when increasing will there be a non-zero H value). H is between [0,100]. This is actually the calculation ...
0
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0answers
60 views

Trying to find parameters for a system of inequalities

So I have a system of 4-dimensional system of ODEs and I'm trying to find any values of parameters that satisfy properties I need. In this picture, I want two basins of attraction, one of which the ...
0
votes
2answers
131 views

Significantly different results between Mathematica and Wolfram Alpha with large radicals and small numbers [closed]

I have some code which involves tiny numbers being put to the power of very large numbers. The function I'm looking at is $\varphi = \omega(T) \left(1 - (1 - \epsilon)^{n_{e}(T)} \right)$ when $\...
3
votes
2answers
225 views

Creepy numerical artefacts of a closed-form solution

I'm wishing you a nice day and here is my problem: I tried to obtain relation between chemical potential and temperature in a semiconductor and I arrived at this equation: $$ 2 e^{-\Delta/kT} \left( ...
0
votes
1answer
92 views

Why does my function return an expression rather than a number? [closed]

I feel like I'm going insane. I have a function $f(x)=e^{-x^2}$ which I need to evaluate using forward, backward and central first order finite differences with intervals ...
8
votes
2answers
332 views

Matching pair of numbers {a,-a}, where a is numeric

Imagine you have a list of pairs of numbers, such as {{2,-2}, {1,5}, {1,-3},{-3,3}} The task is to reduce the given list to a list of pairs of type ...
1
vote
1answer
57 views

Determine whether one value is divisible by another [closed]

How do I determine whether one number is evenly divisible by another in the case of large numbers, for example: 52^52 / 52!
2
votes
2answers
271 views

Center column heading in TableForm

I have a TableForm as follows: ...
0
votes
0answers
26 views

why i cannot get appropriate number with my custom precision? [duplicate]

why i cannot get appropriate number with my custom precision? In[25]:= N[(1 + Exp[-30])/(1 + Exp[-29.9]), 1000] Out[25]= 1. I expect to see a few digits after 1....
0
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0answers
93 views

Numerical Integration/Function

I have a problem with a function defined numerically through an integral of the form: ...
0
votes
1answer
79 views
1
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1answer
104 views

The problem (time) caused by ?NumericQ

In here, I asked a related (similar) question. Using ?NumericQ seems have slowed down the entire calculation. But I now have a more serious problem: ...
0
votes
1answer
92 views

Error with numerical summation - how to specify “n choose r”?

I'm trying to do the following sum: NSum[((50000 - x) choose x)*(1/3^15)^x*((3^15 - x)/3^15)^(50000 - x), {x, 1, 4}] But I keep getting an error saying: ...
6
votes
2answers
901 views

Could I define 0^0 to be 1? [duplicate]

Many occasions, where I need to work numerically with functions. For a variable strictly between 0 and 1, during the optimization, it could become 0.^0 or 0^0, which then become indeterminate. Is ...
0
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0answers
99 views

Speed up numerical optimization (for plotting and solving)?

Briefly speaking, I want to plot a function PIfun[], which its value is based on numerical optimization using NMaximize. It ...
3
votes
1answer
118 views

Inverse prediction function

I am trying to write a code which learns a data set. Now, I want to know the input value for a given output value. Consider, the following code ...
7
votes
2answers
241 views

Why does N[Re@f] give complex result?

Consider this code: ...
1
vote
1answer
49 views
3
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1answer
124 views

Dealing with square roots [duplicate]

Consider following expression: $$ \sqrt{-\left(2 \sqrt{x^{-8/3}-x^{-4/3}+1}\, x^{4/3}+5\right) x^{4/3}+4 \sqrt{x^{-8/3}-x^{-4/3}+1}\, x^{4/3}+2 x^{8/3}+5} $$ In code: ...
0
votes
2answers
67 views

Eigenvectors inside a maniupulate function

I am trying to make a physics application and it requires that the eigenvectors be taken for a 3x3 matrix. It is my intention that Mathematica never have to deal with the matrices symbolically. ...
1
vote
1answer
96 views

Why does one Monitor expression work while another fails?

I have a (somewhat involved) function f[x?NumericQ, y?NumericQ] and for some reason it behaves differently when given a Table ...
0
votes
3answers
476 views

Why is 1. x (Times[1.`, x]) not simplified to x?

This is maybe a silly question, but I could not think of any logical reason why it is not simplified automatically. I was working with a big linear equation system with some constrained inequalities ...
4
votes
1answer
81 views

Strange NSum behavior for slightly larger number of terms

For some sums, NSum gives me the result nicely for some number of terms, but if I add one more term, it suddenly becomes much slower. I haven't found the minimum example for which this can be ...
0
votes
1answer
205 views

FindRoot for numerical function and how to search more than one root

I have to find the first few zeros of function for which I have not the analitycal expression. The function is named f in the following code and it is the result of ...
1
vote
1answer
39 views

Numeric values from transform

How would I create a table of values from a transformation? eg: ...
1
vote
1answer
187 views

Why is Mathematica not able to calculate more digits [duplicate]

When I want a numerical value with a precision of 50 digits... N[1.15/(1 - E^-0.2)^2, 50] Why is Mathematica not able to provide the desired solution? And I ...
2
votes
2answers
272 views

Display truncation of numerical values when writing to a file

I am trying to copy some numerical values of parameters from a plain text file into Mathematica, then arranging them in a list and exporting them to another text file, with .ini extension. My problem ...