Questions about the use of built-in Mathematica functions, including pure functions.
0
votes
1answer
66 views
Can I force a function to quit and return some value after a certain amount of time has passed during its evaluation?
Imagine I provide some random input to function like FindInstance[], and I observe that, despite the existence of good solutions, the function will, with some ...
0
votes
1answer
132 views
How do I define the domain of a function?
I have a function of two variables, f[x_, y_], and I would like to restrict the domain to values of x and ...
-1
votes
3answers
209 views
Sqrt — how to get negative branch?
One of the many attractions of Mathematica is that integers are generally treated as exact symbolic entities, and not just as numbers. I was just playing with Sqrt, and was puzzled by what appeared to ...
3
votes
3answers
220 views
How to sum over a List
list = {11.5575, 11.397, 5.52734, 4.0878, 2.54815, 1.86652, 2.55028,
2.14952, 1.6242, 1.34117}
I have a list of numbers. How do I make a function that creates a ...
0
votes
1answer
80 views
Using undefined function in an expression
I want to use undefined functions in expressions to be simplified. For example.
I want mathematica to simplify this input
$(f^{\prime\prime}(t),g^{\prime\prime}(t))\cdot (-g^\prime(t),f^\prime(t)) $
...
1
vote
1answer
118 views
3D plot of two 2D functions
I would like to plot two 2d functions in a 3d coordinate system. Examples are z = x^2 and z = y^2. Each function has one ...
2
votes
2answers
70 views
changing a symbol into a function variable
Struggled for a while on this problem and hopefully you can help... I have a mathematical expression that currently has a symbol where I used to have a function variable. How do I make the symbol ...
0
votes
0answers
26 views
How does Plot evaluate its argument? [duplicate]
I have a list of about twenty InterpolatingFunctions that I'd like to plot. They are interpolations from experimental data (frequency spectra between 100 and 5000 ...
1
vote
1answer
122 views
Plotting a complex function [duplicate]
What does it mean if this message appears:
{Im[(1-E^Times[<<3>>] f)/(1-Power[<<2>>] f)]-0,Im[(1-E^Times[<<3>>] f)/(1-Power[<<2>>] f)]-0} must be a list of equalities or ...
5
votes
5answers
352 views
Series expansion in terms of Hermite polynomials
I am trying to expand a polynomial in terms of orthogonal polynomials (in my case, Hermite). Maple has a nice built-in function for this, ChangeBasis.
Is there a ...
8
votes
4answers
205 views
Transform a list of functions to a composition
How do I apply a list of functions in a nested way?
Example:
functionList = {f1,f2,f3}
RequiredCommand[functionList,Pi]
such that the required command returns
...
2
votes
1answer
77 views
0
votes
0answers
67 views
FindMaximum inconsistency
The code below seems to work for n<11. But for n=11, and above, it outputs newa then just outputs "beep" sound.
WhyTheBeep says "The kernel Local has quit ...
-1
votes
1answer
88 views
Should Read[] not close its Stream? [closed]
I read a record from a file.
Read[file,Record];
It reads and opens a stream.
Should Read not close its stream after ...
2
votes
3answers
117 views
Alternative to using global variables in functions?
Often times I find myself using unevaluated variables (i.e. they show up blue) as dummy variables in whatever I'm returning such that I can evaluate them as needed later on.
A simple example is as ...
12
votes
3answers
253 views
Accessing list elements by name
First, a bit of a long introduction to my problem:
I only have a few weeks of Mathematica experience. I am creating a mathematica application that calculates some material properties of steel based ...
2
votes
0answers
97 views
Is there documentation on the comparative performance of Mathematica functions?
Recently I have been solving some Project Euler problems. I find there are always several ways to do the same thing. For example, one could join two lists like this:
...
11
votes
1answer
196 views
Is there a summary of answers Head[] can give?
Sometimes you need to check for the type of an expression. You use Head[data] to get answers.
Some data:
...
0
votes
1answer
62 views
how to generate functions with changing array size?
I want to write a function in Mathematica which has two inputs 'n' and 'd', and the output should be (in Latex notation)
$$F(n,d) = \sum_{i[1],...,i[n] =0; i[1]+...+i[n]\leq d}^{d} C[i[1],...,i[n]] ...
1
vote
1answer
114 views
Define a color function using Piecewise
How can I define a ColorFunction for my ContourPlot using Piecewise? For example after ...
9
votes
5answers
334 views
Building a continued fraction
I've completed a problem that involves approximating $e$ by a continued fraction:
$$\frac{N_1}{D_1+\frac{N_2}{D_2+\frac{N_3}{\ddots+\frac{N_k}{D_k}}}}$$
with the $N_i$ being the list ...
0
votes
2answers
177 views
Expansion in Basis Functions
I am trying to create an expansion of the form
f[x,y]->Sum[Cn[x] y^n,{n,1,order}]
To replace the function f by the ...
0
votes
1answer
106 views
Solving a differential equation for a variable in a function
This may sound like a very trivial question, but I need to solve a differential equation as follows:
...
9
votes
2answers
155 views
How can I get the right hand side of a delayed expression?
Imagine there is a given function f, defined with SetDelayed, say
f[x_] := Sin[x]^2 + Cos[x]^2.
Is it possible to get rhs of ...
0
votes
0answers
22 views
Define a Plot3D function with custom options [duplicate]
I am trying to define a Plot3D function with custom options, following (this previous SE question), but I'm running into a brick wall. I've narrowed the problem to the following 'toy' code:
...
4
votes
2answers
127 views
0
votes
1answer
222 views
How can I define a Step-Wise function in Mathematica (Not using Heaviside Step Function)? [closed]
I need to define a function, which has very different behaviour in different regions. There are about 13 different regions. A sample of my function is the foloowing table:
I want to define it as a ...
0
votes
0answers
78 views
Choosing the appropriate solution for the square root [closed]
My problem is the following: given the function
myfunc[x_, a_]:= (a^3 - (a^2)^(3/2))/(x)
the limit as x goes to 0 should be well defined and = 0. However,
...
1
vote
0answers
39 views
Confusing efficiency and evaluation when returning pure functions? [duplicate]
I have a function that takes some time to evaluate, that's meant to be a polynomial approximation to a function. The polynomial is defined by a list of coefficients, so I have the function ...
14
votes
4answers
587 views
Finding Limits in several variables
Is there a way to find a limit of a multivariable function, like
$$\lim_{(x,y)\to (0,0)} f(x,y)$$
with Mathematica?
When $f$ is continuous, we can use
$$\lim_{(x,y)\to (0,0)} ...
1
vote
2answers
64 views
Named patterns as function argument descriptors
I have a function timeToMinutes that takes a 24-hour time as a string argument (in digital clock format, e.g., "15:47") and converts it to the number of minutes ...
0
votes
2answers
111 views
Self-defined function to transform row vector into column vector, where am I wrong? [closed]
I defined a function row2col[] to transform row into column,
Where am I wrong?
...
2
votes
1answer
153 views
Problem using the DifferentialEvolution method of NMinimize [closed]
I have a function of 20 parameters, which 3 of the parameters are my physical parameters, and the others are pull terms to fix the errors. The goal is finding the global minimum of this function, to ...
2
votes
3answers
210 views
How make f[{x,y}] evaluate as f[x,y]?
I frequently encounter the situation where I have a function of two real variables defined, e.g.:
f[x_, y_] := 9 - x^2 - y^2
But then I need to feed into ...
5
votes
2answers
178 views
Is there an $n^{\text{th}}$ root function in Mathematica?
Is there a way to find $\sqrt[n]{x}$ with Mathematica beside of x^(1/n)
as this is something different, because this is not always the same
$$(-1)^{\frac{2}{4}}=i ...
3
votes
4answers
208 views
Extract function arguments
Is there a way to extract the arguments of a function? Consider the following example:
I have this sum
...
3
votes
2answers
227 views
Why does the first derivative of a piecewise continuous function have discontinuities?
I have this piecewise continuous function which is also continuously differentiable over time :
...
5
votes
1answer
94 views
Does pass-by-value affect the performance of function calls?
I only have a little coding experience in C, and I remember I was told that pass by reference is more efficient than pass by value since the parameters don't need to be copied. Since there is no pass ...
2
votes
0answers
144 views
Minimization in mathematica [closed]
I have recently had a strange problem with NMinimize. I have a very huge function with respect to 20 parameters. When I ...
15
votes
4answers
242 views
Enforcing correct variable bindings and avoiding renamings for conflicting variables in nested scoping constructs
Using global variables the following turns an "expression" into a Function:
expr = 2 x;
Function[x, Evaluate[expr]]
Of course ...
1
vote
3answers
186 views
How do I create a matrix of functions?
I'm trying to create a matrix in which the elements are functions of two variables, but I can't figure out how to do it. Is it possible? The only way I could figure out is to define the matrix in ...
2
votes
1answer
117 views
Expression for the real 7/3 power
I need an expression for the real 7/3 power of a real-valued function, i.e., a reformulation of
f[x_] := g[x]^(7/3)
that works for negative values of ...
4
votes
1answer
159 views
A Faster way to combine two Lists of different structures into one of a different structure [duplicate]
I have the following two lists (each containing over 500,000 elements). Here is a sample:
...
1
vote
1answer
108 views
Forcing evaluation of ArgMax
How to force evaluation of ArgMax before its output gets used in Solve?
Background: I'm trying to solve for the Nash ...
2
votes
1answer
106 views
1
vote
0answers
73 views
Solving for vector elements in a function to which the vectors are not passed explicitly
I want to define a function which takes in two integers (indicating the lengths of 2 vectors), and solves a simple set of expressions at a set of points to find all the values in both the vectors.
so ...
1
vote
0answers
73 views
How can I obtain the function described by given set of central moments?
I want to investigate how my function P behaves with different probability functions rho as input variables.
This means
...
1
vote
1answer
119 views
Speeding up code by avoiding repeated evaluation of a function
I want to speed up my code and I have two ideas, but I don't know how I can implement them.
Here is a little part of my code, which I want to improve:
...
1
vote
1answer
108 views
Function definition and delayed assignment
I need to define the following function
MyWavelet[n_]["PrimalLowpass", prec_ : MachinePrecision] :=
Table[(-1)^(j - 1) h[[2*n - j]], {j, 0, 2*n - 1}]
which ...
9
votes
2answers
131 views
Function with custom Options and modified Options for built-in Symbols
I couldn't find a more descriptive title, but I guess an example will explain my problem.
I set up some customized Grid function including some additional ...
