Questions about the use of built-in Mathematica functions, including pure functions.
1
vote
2answers
104 views
How to mix Unevaluated property of function arguments with expression assignments?
This is a follow-up to my (solved) question How to distribute a generic function of two arguments (without evaluating the arguments)
Say, I have a binary function
...
9
votes
3answers
250 views
Why does Hash return different values in Version 7?
This function does not work correctly for me. The generated Gravatars do not match the ones actually produced by using the corresponding address.
The problem was traced to differing output from the ...
3
votes
2answers
538 views
Plot Even Piecewise function
Is it possible in Mathematica to plot an even piecewise function like:
$ f(x) = \begin{cases} 3t , 0 \le t \le \frac{\pi}{2} \\
3t + 6 , \frac{\pi}{2} \le t \le \pi \end{cases}$
which has ...
4
votes
3answers
110 views
How to distribute a generic function of two arguments (without evaluating the arguments)
I guess there is an easy way to do this, but I can't seem to figure it out. What I would like to do is to distribute a generic (i.e. without specifying what this function really does) binary function. ...
1
vote
2answers
70 views
Using non-Graphics primitives when exporting to .cdf
I'm trying to embed a "Manipulate" applet I've created into a webpage by embedding a .cdf. I'm running into a problem with displaying outputs from functions I've written. Here is a simpler example ...
7
votes
1answer
224 views
Demonstrating Ackermann's Function
The Ackermann function is an extremely fast growing function. There are some slightly different versions of the function, but the one that I am looking for can be defined as:
$$
A_0(x)=x+1 \\
...
3
votes
3answers
146 views
How to set a function as a parameter?
In case I want to know whether a given function $f(t)$ have some property, I tried to write something like this:
...
3
votes
3answers
165 views
How to pull scalars out of a function that should act on lists?
Suppose I have
A = a vecA
B = b vecB
where a and b are supposed to be arbitrary scalars ...
3
votes
1answer
345 views
How can I save and recall my own function?
In MATLAB, I can save and recall my own function using an M-File(function or script)
How can I do something similar in Mathematica?
I already searched and know how to define functions and modules ...
3
votes
3answers
346 views
Map w/ multiple arguments [duplicate]
Possible Duplicate:
How do I use Map for a function with two arguments?
If I have a function:
F[x_,y_,z_]:=x*y*z
and I want to call it with several ...
3
votes
2answers
176 views
Plotting two functions with dependent input function
I have defined a function:
myJ2[n_] := 1/n* Total[RandomVariate[NormalDistribution[0, 1], n]^2]
This is basically an approximation to the gaussian integral. I ...
0
votes
0answers
88 views
Skip one step of the loop if there is NIntegrate::eincr: message
is there possibility to skip one step of the loop if in this step there appear error like NIntegrate::eincr:? For example: when I use "do" loop and when one of the step is evaluating I would like to ...
9
votes
2answers
262 views
NestList on a function with more arguments
I'd like to know if it is possible to use NestList on a regular function with more arguments, such as:
...
2
votes
1answer
411 views
Nested If statements
When I do this:
Apply[(If[#2 == what, "yay", If[#2 == whoops, "nay"]]) &, {-5, what}]
I get:
yay
But when I do this:
...
3
votes
2answers
133 views
Handling Indeterminate Forms
I'm running a sum, the elements of which are calculated by calling functions that I wrote. The only issue is, I've implemented this pretty stupid solution where I have 4 or 5 (nested!) if statements ...
4
votes
1answer
195 views
How to organize and run functions?
I am very new to Mathematica. I thought I would try it out for my first assignment in my computer science class. Until now I have only used C-base languages including C#, Java, Objective-C, and ...
8
votes
1answer
233 views
ReplaceAll[] and Limit[] don't give correct results for this expression under extreme variables [duplicate]
Possible Duplicate:
Funny behaviour when plotting a polynomial of high degree and large coefficients
1/x^2 + (3 + x)/(6 (1 - Exp[x] + x))
——This is a ...
1
vote
1answer
148 views
Computing a logarithmic function
Possibly this is a very lame question for this site.
There is a function $f(n)=-\ln(a*n); \space \Bbb Z \to \Bbb R$, and I want to define $a$ for pairs of values. For example:
$f_1(n_1)=15; ...
4
votes
4answers
390 views
How to define and use a linear function
I have the following equation $T = -800n + 12000$.
I know that this is a linear function and that the two points $(0, 12000)$ and $(15,0)$ lie on the line.
When I have 2 other values of n between 0 ...
9
votes
5answers
670 views
Counting negative values in list
I would like to count the negative values of a list.
My approach was Count[data, -_] which doesn't work.
How can I tell Mathematica to count all numbers with ...
1
vote
2answers
182 views
Piecewise function with a function as argument
I want to define a piecewise function, which has two arguments, one of which is a function of the other's piecewise argument. I am giving an example
...
1
vote
2answers
101 views
How can define a set of nested parameters
I would like to know how I to define a function with a nested set of parameters (or whatever you would like to call it). For example, how would I get the following function ...
1
vote
1answer
110 views
Using an InputField to define a function to compose with a sequence
I am still trying to figure out Mathematica (started early August). I am trying to write a program that will accept an arbitrary function and an arbitrary sequence that can start at an arbitrary ...
5
votes
3answers
226 views
First evaluation fails
I am fairly new to Mathematica (version 7), so please bear with me...
I have duplicated, in Mathematica, a program that I originally wrote in C (it generates OEIS sequence A191837). The problem is ...
16
votes
8answers
422 views
Applying And to lists of Booleans
I'd like to take {True,True,False} and {True,False,False} and apply And to get ...
13
votes
7answers
318 views
Get the first element after the first sequence of length N of consecutively increasing values
I'm looking for an efficient way of extracting the first element after the first sequence of N consecutive elements in which the values are increasing.
If these are the data of a toy example:
...
7
votes
2answers
225 views
Determine whether some expression contains a given symbol
Given a symbol t and an expression expr, how can I determine whether or not the symbol t ...
1
vote
1answer
103 views
How to explain the results of the following integrals?
Why does the following program lead to different results of a21 and a211?
...
2
votes
3answers
195 views
How can `SquareWave` be used as the input in `OutputResponse`?
I'd like to compute the response of a TransferFunctionModel when driven by a SquareWave. Here's a simple example,
...
4
votes
2answers
245 views
Implementation of builtin function Fold
In the documentation for fold, it says
Fold[f,x,list] gives the last element of FoldList[f,x,list].
But this is surely not the way it is implemented, right? ...
7
votes
1answer
187 views
RootSum result manipulation/simplification
Consider the sum
sum1 = Sum[ k/( k^7 - 2 k + 3), {k, Infinity}]
...
8
votes
1answer
375 views
GeoDirection and GeoDistance Memory Leaks: How to Recover the Memory?
The functions GeoDirection and GeoDistance have memory leaks. To see this, run the example functions below and watch as the Physical Memory Available in the Windows Task Manager, Performance tab, ...
3
votes
2answers
185 views
How does RootOfUnityQ work?
How does Mathematica's RootOfUnityQ function work?
That is, how does Mathematica know if a number is a root of unity?
Example:
Let $x = \frac{1-i \sqrt{2+\sqrt{5}}}{1+i \sqrt{2+\sqrt{5}}}$.
Then
...
3
votes
1answer
150 views
Evaluation of self-defined functions
I defined a function that I call disc which I want to minimize later. The function is defined as
...
-5
votes
3answers
258 views
Constructing lists by applying functions to another list
Suppose f is a function of two variables: $f = f(x,y)\quad$ and $L$ is a list. Could someone help me in defining a list of the form:
$D = \{f(x,y)\ |\ x \in L,\ y \in L\}$
I tried this:
...
11
votes
4answers
283 views
Assessing argument type in set delayed function definitions
I'm wondering how to properly assess the type of arguments passed to functions defined with :=. I want my functions to be the most efficient, unambiguous and clear ...
-1
votes
1answer
157 views
Why is the CTRL + / not working?
I've learned how to use this shortcut to input fractions in the 2D form, it worked nice on my notebook but I can't make it on my desktop. Any tip on what could be happening?
8
votes
2answers
223 views
Sum or Product with Exclusions
Is there a built-in feature for handling things like:
$$\sum_{i=0}_{i\ne j}^n\frac{a-a_i}{a_i-a_j}$$
and
$$\prod_{i=0}_{i\ne j}^n\frac{a-a_i}{a_i-a_j}$$
or should I work out some sort of Do ...
1
vote
1answer
178 views
How to substitute variables in interpolated function?
I'm looking for the way to substitute variables in interpolated function again to original one.
(I want to know how to get P(r, theta) from Psol(v, w).)
The original variables :
...
0
votes
0answers
154 views
How Can I Use Conditional with Rational Domain Restrictions
I am reasking this question in a new thread. My previous post How Can I Use Solve/Reduce Output? seemed to have led to a an interesting dissussion of how to (better) solve the problem that produced ...
4
votes
1answer
359 views
How Can I use Solve/Reduce Output
Suppose I want x and y to be rationals
Solve[ x^2 + y^2 == 1, {x, y}, Rationals]
I am ...
4
votes
2answers
270 views
Evaluating an If condition to yield True/False
I would like to decide whether an option passed to my custom function has the value Automatic or something else. This is my attempt:
...
6
votes
3answers
153 views
Get unevaluated option value?
This is kind of a follow-up to this question.
I want to be able to define a function that takes an option, and then, inside the function, retrieve and test the unevaluated value of the option. For ...
3
votes
0answers
85 views
ProbabilityDistribution PDF on boundary points
I would like to evaluate the PDF of a custom ProbabilityDistribution at the min and max values. However, PDF[...] returns 0 at ...
6
votes
2answers
379 views
Pass function or formula as function parameter
I can write either
Integrate[x^2, {x,0,3}]
or
f[x_] = x^2
Integrate[f[x],{x,0,3}]
and get the same computation. Suppose I ...
6
votes
2answers
411 views
Speed up Mathematica code involving Convolve
I'm trying to plot the averaged autocorrelation function of a random wire profile $\xi(x)$ which is build from unitsteps which are each L units long. To calculate the average I'm generating nMax ...
4
votes
1answer
285 views
What is the difference between Set and SetDelayed?
I have a problem with defining a function and most of time I get confused by Set or = and ...
18
votes
1answer
266 views
What does “EquationalLogic`FindCounterexample[]” do?
I found the undocumented EquationalLogic`FindCounterexample[] by browsing the lists of available symbols, but I have no clue about its purpose.
The name is ...
2
votes
1answer
327 views
Function output from DSolve
I want to get a function as output form DSolve.
For Example :
sol = DSolve[{Q''[t] + 40 Q'[t] + 625 Q[t] == 100*Cos[10*t], Q[0] == 0, Q'[0] == 0}, Q[t], t]
I ...
6
votes
2answers
415 views
Finding all partitions of a set
I'm looking for straightforward way to find all the partitions of a set.
IntegerPartitions seems to provide a useful start. But then things get a bit complicated.
...
