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0
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2answers
83 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
votes
0answers
42 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
0answers
4 views

How to write this Google docs, percentage calculation function? [migrated]

I track my diet (macros) in Google docs. For 1 day my protein is 114.63 carbs 194.75 and fat ...
0
votes
2answers
85 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
190 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
77 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
270 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
53 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!
1
vote
2answers
119 views

Center column heading in TableForm

I have a TableForm as follows: ...
0
votes
0answers
25 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 ...
0
votes
0answers
84 views

Numerical Integration/Function

I have a problem with a function defined numerically through an integral of the form: ...
0
votes
1answer
69 views
1
vote
1answer
91 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
46 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: ...
1
vote
1answer
69 views

How to indroduce a value for the functions inside a matrix? [closed]

I would like to assign certain values to the X and Y variables which are inside the functions in the matrix. Thus, I would like to get a matrix with values based on the transformation in Psi matrix. ...
0
votes
0answers
76 views

Different kind of numeric erros when plotting recursive functions

I have been trying to plot some numeric solutions to a Hamiltonian system. Basically I have ...
6
votes
2answers
619 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
votes
0answers
74 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 ...
2
votes
4answers
210 views

Problem in finding the numerical maximum

I need to find the numerical maxima of the function $$i(s)=\bigg[ \frac{\sin{50\pi (\cos s+1)}}{\sin{10\pi (\cos s+1)}} \bigg] ^2$$ Or in the mathematica input form: ...
1
vote
0answers
65 views

Central binomial coefficient [closed]

I am tasked with creating a recursive definition of the binomial coefficients that stores previously calculated values. this is what I have: ...
3
votes
1answer
106 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 ...
4
votes
2answers
200 views

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

Consider this code: ...
1
vote
1answer
47 views
0
votes
0answers
171 views

Could not solve a set of equations with available mathematica tools

The problem I described below is an simplified way of expressing it.(Sorry that I still did not figure out a way to copy the code to here.) The actual equation is like What I am trying to find is ...
3
votes
1answer
102 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
63 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
86 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
216 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 ...
3
votes
1answer
60 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
156 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
35 views

Numeric values from transform

How would I create a table of values from a transformation? eg: ...
1
vote
1answer
151 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
209 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 ...
0
votes
1answer
237 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: ...
4
votes
2answers
590 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 ...
6
votes
1answer
95 views

Machine precision infinity

Is it possible to obtain the machine precision (double) version of Infinity? This is useful when using LibraryLink and C ...
1
vote
1answer
120 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 ...
3
votes
3answers
208 views

FindRoot constrained to maximum

I am using FindRoot to find the local maximum op some function, by examining where its derivative is zero. However, keeping the starting value the same, sometimes ...
2
votes
3answers
348 views

Re-arranging / selecting of a data table very slow in For loop [duplicate]

My task is quite simple; I have a table of data like M = {{1,2}, {1,3}, {3,4}, {5,1}, {6,9}, {6,8}, {6,1}}; so the table is sorted with respect to the first ...
3
votes
1answer
210 views

Fixed-Point Numbers in Mathematica

I am working with a library that needs input in a Fixed Point notation. I’d like to figure out a way to convert the floating point results into fixed point representation. The fixed point length is ...
1
vote
2answers
181 views

How to make a single-variable out of a NDSolve solution?

So I've got this line that contains the solution of a partial, non-extraordinary differential equation (because Mathematica doesn't handle extraordinary partial differential equations): ...
0
votes
1answer
509 views

How to use NIntegrate in a function using parameters from a list

I would like to use NIntegrate in a function with some parameters from a list. I simplified my problem for this forum. The list of parameters is as follows: ...
4
votes
1answer
221 views

DensityHistogram label/display values in Mathematica 8

I'm trying to make a DensityHistogram in Mathematica 8 that overlays the histogram values for each location. What I want is for the value of each square to be ...