Questions tagged [functions]

Questions about the use of built-in Mathematica functions, including pure functions.

296 questions with no upvoted or accepted answers
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80 views

Using While properly

I am trying to make While[] work with function results and evaluate them at the same time. ...
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34 views

Convolve[…] behaves differently to that of Integrate[…] when numerically integrating the result

I am performing a convolution between two functions, and then I want to numerically integrate the result. If I go: ...
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115 views

Help! SystemException[“MemoryAllocationFailure”]

I am trying to run this code: ...
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38 views

Calculate with general discrete probability functions?

I would like to work with a discrete probability function $P[x\_]$ that only has the property that it is defined for $x\geq0$, such that Sum[P[x],{x,0,Infinity}] ...
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36 views

Problem in importing function in NDSolveValue

I have a code for solving a system of 2 differential equations (sol1). Given that what's inside is a bit heavy, I define functions so that I can call them. My issue is that when I write everything ...
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72 views

Is there a way to order the QZ(or Gen. Schur) decomposition in mathematica?

Let's imagine I have two matrices $\Gamma_0$ and $\Gamma_1$. The SchurDecomposition function in mathematica will return matrices $Q,\Lambda, Z, \Omega$, such that $...
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71 views

Recursive functions with integrals/derivatives return wrong results

I have the following recursive functions: ...
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47 views

Multiple Square Bracketed Function definition

I am familiar with the typical way of defining a function--such as f[x_,y_]:=x+y but I have not found a discussion of definitions such as ...
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89 views

Function that Generates all Normal Subgroups of a Group

I am trying to create a function which, given a group structure, generates a list of all the normal subgroups contained within it. But I am not sure how to proceed. For now, I have the following: <...
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38 views

Store a matrix function for a particular value of its argument and use it without calling the function again?

Suppose I have defined a function as: f[x_]:={{x,x^2},{x^3,x}}; g[x_]:=f[x][[1,2]]+f[x][[2,2]]+f[x][[2,1]] Now if I want to calculate ...
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75 views

Take double integral

I'm trying to take a double integral: $\int_0^1\int_0^1 \left[\left(\tilde{B_V}(\alpha_V) \{||\}(\tilde{B_V}(\alpha_V) > \tilde{B_A}(\alpha_A) - 1 - \theta(1 - r))Z\right) + \left(\tilde{B_A}(\...
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140 views

Newton's method for nonlinear equations system

My code is: ...
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76 views

Dynamic Passing Function as Argument

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77 views

Possible bugs with InverseFunction in version 11.2

See these two examples ...
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48 views

How to handle functions with varying number of arguments

Suppose I have a function that depends on variables $x_1, ... , x_n$. For concreteness I may have $f(x) = v \cdot x$, with $v$ a certain vector. Now I want to do certain operation with this function, ...
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86 views

Mathematica can't evaluate the function at the point where it is smooth

Suppose the function ...
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80 views

Operator on a multivariable function in a sum

I need to define an operator that does as follow for any function $h_m$. $\qquad O[h_m](k,M,b,l_{max})=\sum_{l\neq (0,m)}^{l_{max}}il \left (h_l(k,M,b,l_{max}) b_{m-l}(k)- c_l\partial_k h_{m-l}(k,M,...
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0answers
84 views

Using Two Arguments on the Same Function

I'm having some trouble wrapping my head around how I would go about using two arguments in one function. In the first section of the code below, I have scraped some "tweets" on the Seeking Alpha ...
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0answers
179 views

Solve a system of time dependent equations where the Unknown variables are time dependent functions

I have to solve a system of time dependent equations ( $eqf1,eqf2,eqf3,...eqm5,eqm6$, inside the equations there are known time dependent functions) where the Unknown variables ($f32,fe3,me3...f47,m47$...
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86 views

Computationally Employ Sum over Ordered Partitions?

I have the following function defined, with two inputs $g$ and $h$: ...
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93 views

Colorize a 3D plot with given function of dependent variable and add a bar legend

I want to colorize a surface $u(t,x,y)$ generated by Plot3D with a given function of $u$. For example, ...
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0answers
58 views

Same functions in plot but in different ways get different graph

According the documentation in Wolfram, Plot uses in below way, Plot[f,{x,xmin,xmax}] So, there is my original code. ...
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0answers
79 views

Very slow Absolute value computation (Improvement need)?

I have to compute the following absolute value. When computing the absolute value of the two pieces separately, everything works fine. When summing up and then evaluating the Abs of the Sum, the code ...
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142 views

Find the relations between two parameters

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41 views

FinancialDerivative with a delayed start

Using the function FinancialDerivative with an Asian style option doesn't seem to have a parameter that allows for a contract that averages over a specific time period in the future rather than over ...
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0answers
92 views

Convolve returns false result

Bug introduced in 9.0 or earlier and fixed in 10.0 I tried to convolve sin with sin and got this unexpected result: Convolve[Sin[x], Sin[x], x, y] (* 0 *) Now I ...
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55 views

Different Derivative's output with ComplexExpand

Consider this expression f = Abs[ x + I ] with this assumption $Assumptions = Element[x, Reals] Now there is something ...
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82 views

Plotting Asymptotic Series

I apologise for being always here asking for the same questions, but I need to learn. I have to plot this series $$\frac{\pi}{2} - \frac{\cos x}{x}\left(\sum_{k = 0}^{+\infty} (-1)^k \frac{(2k)!}{x^...
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48 views

Extracting elements with a certain criteria from a pre existing list

Here I take just a random list of triples of size 10 ...
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0answers
113 views

ListDensityPlot erroneously showing flat regions (NOT plot range issue)

I have a dataset (listed below). I'm trying to plot the dataset using ListDensity plot; ...
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414 views

Defining a piecewise function where the conditions are points

I am trying to define the following function in Mathematica: $$pw=\begin{cases} x y \cos \left(\frac{1}{x^2+y^2}\right) & (x,y)\neq(0,0) \\ 0 & (x,y)=(0,0) \end{cases}$$ I want to use this ...
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0answers
280 views

An array of functions

I need to define an array which every entry is a function. To be more specific, I want to solve the equation: $$\frac{d \rho}{dt} = -i[H, \rho] + L[\rho]$$ in which $\rho$ is a matrix. This is a ...
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0answers
726 views

Polar to Cartesian and Cartesian to Polar Transformation

I have noticed some odd behavior when converting from Polar < -- > Cartesian. For example; https://math.stackexchange.com/questions/290209/diff-eq-transformation-polar-coordinates We want to ...
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0answers
78 views

The wire frame from a Plot3D gives a jumbled mess for a wire frame

Some time ago I found a post that turned the triangles of a mesh into polygons. I have spent 2 hours looking for that post and can not find it. The problem: Plotting ...
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0answers
259 views

How to get user input using FormPage

I am designing a user interface for a word-ladder game using CloudDeploy, CloudExpression and FormPage and I am having trouble with receiving the user input from the form. What I basically need is a ...
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0answers
56 views

Is there any point to using a variable as a function parameter?

Normally one only sees patterns as function parameters: fun1[x_]:=x^2 Is there any point to using a variable in a function definition: ...
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0answers
38 views

Function with many lines that takes image as parameter not returning same result as if I run the same lines of code

Running the exact same lines of code in a function produces just a return of the original image without any points identified, whereas when I run the exact body of the function line by line it works ...
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0answers
83 views

Finding correct combination of functions

I am trying to write code where I have an array $S$ or numbers in any order [5,4,2,1,....] Then I have a specific set of functions that I can write. ...
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0answers
191 views

Help with calculating a complicated integral

Edit: The question is solved : )) Thank you for your attention ! I am sorry for mass questions, but the question bothers me a lot. So I would like to ask this question here. This problem arises when ...
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0answers
51 views

When evaluating this integral Mathematica returns two different answers

When evaluating this integral in Mathematica 10.3 Student Edition: ...
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0answers
46 views

Defining an object which is function in some variables and tensor in some other indices

I am trying to define an object which function in some variable and tensor in other indices. My attempt at it was: ...
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0answers
106 views

DiracDelta of a function

If I have, for instance, FunctionExpand[DiracDelta[x^2+x-3]] it evaluates to ...
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87 views

Which method to use for finding maximum without actually computing optimization function explicitly?

I am new to Mathematica and I am currently working on an optimization problem. The optimization function that I have easy to calculate for some assignment of variable but it is very difficult to ...
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0answers
258 views

How to simplify an expression with a radical sign nesting in a radical sign

Is there a function can simplify an expression with a radical sign nesting in a radical sign in Mathematica? I use V9. RatDenmon is a function that can ...
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0answers
74 views

Input `Reduce[Mod[a + x, l] == 0, x]' and output `x == -a + kl`?

Reduce[a + x == k l && k > 0, x] (* k > 0 && x == -a + k l *) I think a + x == k l and ...
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0answers
100 views

What are the differences between these functions when used for NMaximize?

In short, the question is how to construct the function you want to optimize? ...
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0answers
100 views

Improving RationalInterpolation Result

The following code produces a {4,4} rational interpolation approximation accurate to 10^-6 or better over the range ...
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0answers
493 views

Crosscorrelation for nonperiodic signals

I want to detect patterns (of an absorption spectrum which is nonperiodic) with Mathematica automaticly. I have found CorrelationFuncion but as far as I understand, ...
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0answers
256 views

RowReduce doesn't work for this matrix?

I have this matrix A={{0,1,1,w},{1,0,1,x},{-1,0,1,y},{0,1,1,z}} where w, x, y, z are arbitrary constants. This matrix should be row reduced to the form ...
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0answers
62 views

Is it possible to calculate with declarations only?

simple Example: maximize $u(x), x$ solution would show constraints: $\frac{\partial u(x)}{\partial x} = 0$ $\frac{\partial^2 u(x)}{\partial x} < 0$ etc... or do I always have to explicitly ...