Questions about the use of built-in Mathematica functions, including pure functions.
52
votes
6answers
3k views
List of compilable functions
Is there somewhere a list on the functions that Compile can compile, or the cases in which a particular function can be compiled that I haven't found?
I'd be glad ...
47
votes
3answers
694 views
Automatically generating a dependency graph of an arbitrary Mathematica function?
Has anyone written a function to pull the function dependencies of a function? That is, it would be nice to have a function that returns a list of function dependencies as a set of rules, terminating ...
40
votes
2answers
822 views
Flatten command: matrix as second argument
One thing I could never wrap my head around is how Flatten works when provided with a matrix as the second argument, and the Mathematica help isn't particularly ...
30
votes
2answers
771 views
What is the difference between Reduce and Solve?
Solve and Reduce both can be used for solving equations.
Just by operating them, I know there is little difference between them.
But, the only thing I know is that there is little difference, and I ...
29
votes
2answers
3k views
What is so special about Prime?
When we try to evaluate Prime on big numbers (e.g. 10^13) we encounter the following issue :
...
28
votes
2answers
505 views
Variable naming changes everything
I am having a rather unusual problem I do not understand with Mathematica where renaming one of the variables of my function causes the function to stop "working". Here is the example of the code ...
24
votes
3answers
464 views
Parentheses in pure functions: # & vs. ( # &)
I've been using Mathematica for years, and over time I have developed the habit of using:
Select[data, (# == 1 &)]
instead of
...
23
votes
2answers
684 views
Block attributes of Equal
I answered “Equating matrices (or higher order tensors) element-wise” with:
...
21
votes
4answers
510 views
Why is there no PositionFunction in Mathematica?
Too often I have seen the programs of inexperienced users greatly slowed by using Position in an iterative fashion, when far faster would have been to compute a ...
20
votes
4answers
730 views
Are there “All” and “Any” functions in Mathematica?
In Python, there is a function all which returns true if all of its arguments are true, and any which returns true if at least ...
20
votes
3answers
378 views
Is there a bug in Pick?
I wanted to use the Pick function with a condition. But there seems to be an issue here. Take a look at this:
...
20
votes
2answers
529 views
Strange ::usage behavior in v9
Note: This is fixed in 9.0.1.
Something has gone wrong with usage in Mathematica 9. Would someone tell me how to fix it?
I define a function ...
18
votes
3answers
476 views
How to load a package without naming conflicts?
This question applies to any package, but I encountered this problem while working with graphs.
There are symbols in the Combinatorica package (such as ...
18
votes
1answer
139 views
What does Internal`InheritedBlock do?
What does the function Internal`InheritedBlock do? How is it different from the regular Block?
18
votes
1answer
268 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 ...
17
votes
2answers
391 views
Implementing continuous phase/Arg function
In MATLAB there's a function called phase that is just like our Listable friend Arg, but ...
16
votes
8answers
428 views
Applying And to lists of Booleans
I'd like to take {True,True,False} and {True,False,False} and apply And to get ...
16
votes
3answers
1k views
Plotting piecewise function with distinct colors in each section
I have a piecewise function that I would like to plot but I was wondering if it is possible that each part of the function that is plotted when its corresponding condition is true be plotted with a ...
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 ...
14
votes
4answers
588 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)} ...
13
votes
4answers
922 views
sprintf() or close equivalent, or re-implementation?
Is there a sprintf() command (some command that takes a printf-style format string and a list of values to insert into the ...
13
votes
6answers
880 views
Max of a table/list with indeterminate values
Suppose I have a Table:
tab = {1., 2., 3., Indeterminate}
When I type Max[tab] I get ...
13
votes
3answers
488 views
Can someone explain this snippet: (#[#] &)[#[#][#] &]
A friend showed me this snippet of code today:
(#[#] &)[#[#][#] &]
I can sort of see that we're constructing an anonymous function that takes a function ...
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:
...
13
votes
3answers
199 views
How to keep some of the results of the NestList
I'm using some iterative arithmetics to calculate wave propagation with the help of NestList. I have to use a small step size for iteration to guarantee the accuracy, which lead to too much data (e.g, ...
13
votes
3answers
393 views
Is it possible to get the order of inputs when “overloading” an orderless function?
When working with symbolic matrix operations or other objects which don't have commutative multiplication, it would be nice to not have to constantly switch out times for ...
12
votes
6answers
309 views
Comparing the last output of a nested function with all the previous ones
my main question is how I can compare the last output of a nested function with all the previous ones and stop iterating when I find a repeating value. (I have 2 other questions but I think they are ...
12
votes
3answers
395 views
How to make the suggestion box appear?
When you type a function in Matlab, quickly a suggestion box comes up showing functions similar to the one you're typing. I thought that Mathematica didn't have this but one day, I typed half of a ...
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 ...
12
votes
2answers
289 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 ...
12
votes
1answer
245 views
Function as an option to a function
I am new to mathematica ,so this question may seem a little naive.
I know how to use the option as an argument to a function, we can define an option by using ...
12
votes
1answer
380 views
Error checking and trapping techniques with Throw and Catch
Mathematica provides several mechanisms for checking arguments and trapping errors in a function definition.
Typical methods are :
Definitions with argument patterns, definitions with ...
11
votes
4answers
2k views
How to find the domain and range of a function with Mathematica?
I'm studying calculus and in some exercises I am asked to find the domain and range of a function. Does Mathematica have already a built-in function for this?
I can imagine some ways of doing so, ...
11
votes
4answers
297 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 ...
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:
...
11
votes
1answer
5k views
How to express trigonometric equation in terms of of given trigonometric function?
How can I express a trigonometric equation / identity in terms of a given trigonometric function?
using following trigonometric identities
...
11
votes
1answer
189 views
What's a good style for inheriting Options[] of built-in function?
Options[myPlot] = Options[Plot];
myPlot[args___] := ...
When defining a "wrapper" function like the above, I'd like it to inherit the ...
11
votes
2answers
106 views
What are Root objects with multiple polynomials?
In Mathematica 9 a new flavor of Root object with multiple polynomials was introduced. For example,
...
11
votes
1answer
179 views
Choosing among different function definitions without sacrificing speed
I'm working on some code that numerically integrates a function, let's call it G, which calls another function, F, that can be ...
10
votes
9answers
409 views
How to find range in which a number falls, from given list of numbers?
How can one find the range in which a number falls, from given list of numbers?
...
10
votes
5answers
710 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 ...
10
votes
3answers
377 views
How to modify function argument?
Usually in programming languages, function arguments are normal local variables, which can be modified.
Is this not true in Mathematica?
...
10
votes
2answers
359 views
How do I find the elements in a list that return the highest value for a function?
Suppose we have a list of values and a function f. I want to find which of the elements maximizes the return value of the function in Mathematica. Let call the ...
10
votes
2answers
204 views
Functions that remember their values
Can someone explain what is going on with the following ...
func[y_] := func[y] = (Print["Hello world !!!"];)
func[1]
Hello world !!!
...
10
votes
2answers
458 views
How to add an interpolating point to InterpolatingFunction?
Suppose I have an InterpolatingFunction object defined on $[\epsilon,1]$; let's call it f. What is the best way to construct a ...
10
votes
3answers
211 views
How to “ignore” an element of Map or MapIndexed
Say I have some function that I'm applying every element in a list to... if that element matches some criteria:
...
10
votes
2answers
281 views
How to test if optional argument has been given?
I understand that the last call (f[1]) returns True because arg does not exist and thus ...
10
votes
2answers
97 views
Functions in a different context are replaced with infix forms of their namesake in System`
So, in an attempt to help out Fabian with his question, I did what I often do, and created a new symbol in the Pillsy` package that I could play with. Since it was ...
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 ...
9
votes
3answers
261 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 ...
