# Tagged Questions

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89 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 ...
4 views

### How to calculate a sum using a geometric series [migrated]

How to calculate this with a simple calculator. sum_{i=20}^n=59 0.1*600*1.04^(60-i) = ? I tried this but it's wrong. Can somebody please tell me where I made a ...
90 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 ...
261 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 ...
87 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: ...
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### 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 ...
168 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 ...
61 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. ...
38 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 ...
53 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?
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### 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 ...
328 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 ...
56 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!
257 views

### Center column heading in TableForm

I have a TableForm as follows: ...
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### 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 ...
92 views

### Numerical Integration/Function

I have a problem with a function defined numerically through an integral of the form: ...
79 views

### Difference Eigenvector values in mathematica 9 and mathematica 10 [duplicate]

I have the following matrix; ...
101 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: ...
87 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: ...
868 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 ...
94 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 ...
115 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 ...
239 views

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

Consider this code: ...
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Let ...
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### 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: ...
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. ...
95 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 ...
458 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 ...
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 ...
203 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 ...
39 views

### Numeric values from transform

How would I create a table of values from a transformation? eg: ...
180 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 ...
269 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 ...
365 views

### NMinimize holding problem

I have a function that I want to minimize numerically through an NMinimize command (because it's very complicated analytically). The minimizer call looks as follows: ...
651 views

### Why are my recursive functions running so slowly? And how do I fix them?

I am working with making numerical solvers for a modeling class I am in, and I want to use the internal recursion handling that is built into mathematcia, but there seems to be a problem. NDSolve ...
111 views

### Machine precision infinity

Is it possible to obtain the machine precision (double) version of Infinity? This is useful when using LibraryLink and C ...
181 views

### How do assign an interval of values to a variable in order to use them in a function?

From my code (below) I have K1 and K2 set to zero in order to test this numerical method. However, K1 is on an interval from 0 to 32, and K2 is on an interval from 0 to 8. I would like to know if ...