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

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12
votes
5answers
1k views

How to completely delete the head of a function expression

Is there any way to completely remove the head of an expression function? For example, how would I remove the head Cos from ...
12
votes
5answers
10k views

Calling Correct Function for Plotting DiracDelta

I am wondering what is the correct function in Mathematica to plot the true impulse function, better known as the DiracDelta[] function. When using this inside of a ...
11
votes
3answers
245 views

How to deal with the condition $u_i=u_{i+1}$ in B-Spline basis function?

The defintion of B-Spline basis function as shown below: Let $\vec{U}=\{u_0,u_1,\ldots,u_m\}$ a nondecreasing sequence of real numbers,i.e, $u_i\leq u_{i+1}\quad i=0,1,2\ldots m-1$ $$N_{i,0}(u)= ...
8
votes
2answers
2k 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. ...
28
votes
2answers
927 views

Strange ::usage behavior in v9

Bug 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 ...
7
votes
4answers
3k views

“do … while” loop equivalent in Mathematica [closed]

Have I missed something or is there no built-in which mimics the behaviour of do ... while loop? I am looking for a construct that evaluates procedure once and ...
3
votes
2answers
382 views

Permanently rounding numbers/values to a given number of significant figures

I am searching for a simple way of rounding and setting an input to a desired number of significant figures. There are a vast number of posts that discuss similar problems, but none address this ...
3
votes
1answer
313 views

Call Functions From File Without Modifying Context (Sandbox)

Let's say I have file named test.m containing test[arg1_] := ( Print[arg1];) What is the best technique for calling test like ...
8
votes
3answers
799 views

FullSimplify does not work on this expression with no unknowns

I can't reproduce this simple example from Habrat, 2010 ("Mathematica : a Problem-Centered Approach"). It is supposed to demonstrate the functionality of ...
7
votes
5answers
394 views

Is it possible to insert arguments into functions when they're used like Function@ or //Function?

Is it possible to insert arguments into functions when they're used like Function@ or //Function? Sometimes I need to do this, but then I have to return to the standard function usage: Function[] ...
6
votes
4answers
560 views

How can I get the number of slots in Function?

Suppose that I define f = Function[#1 + #2]; And I want to define a new function, argsNum, so that it returns a number of ...
1
vote
4answers
3k views

Solve trigonometric equation

I'm looking for a solution (graphic, numeric or analytic) for a function of the form: $$a^2\tanh(x)=\tan(ax),\quad a ≥ 1,\ x > 0$$ preferably using Mathematica. Any advice?
9
votes
3answers
888 views

Inverting a function in a certain region

InverseFunction works well for globally invertible functions, like f = 2*# + 2 &; InverseFunction[f] ...
7
votes
5answers
4k 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 ...
2
votes
1answer
189 views

Why evaluation doesn't fail if arguments are invalid? [duplicate]

Sorry for a noob question, but this is something that I wonder about each time I work with Mathematica. Coming from standard programming languages (Python and Java), I expect my functions to fail ...
36
votes
2answers
1k views

Variable naming changes everything

Bug fixed in 10.0.0 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 ...
28
votes
1answer
364 views

What does Internal`InheritedBlock do?

What does the function Internal`InheritedBlock do? How is it different from the regular Block?
20
votes
4answers
969 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
1answer
830 views

user defined functions, how to save them for future use?

I need certain user defined functions over and over. I was wondering how can I define and where and how to save them such that each time I start a notebook, these functions are available and need not ...
25
votes
1answer
475 views

In 10.1.0 BenchmarkPlot doesn't work?

Bug introduced in 10.1 This bug was resolved in 10.2.0, but another bug was introduced in 10.3.0 which persists through 10.3.1 or later In Mathematica 10.1.0 and 10.3.0 ...
17
votes
2answers
2k views

Sum or Product with Exclusions

Is there a built-in feature for handling things like: $$\sum_{\substack{i=0\\i\ne j}}^n\frac{a-a_i}{a_i-a_j}$$ and $$\prod_{\substack{i=0\\i\ne j}}^n\frac{a-a_i}{a_i-a_j}$$ or should I work out some ...
22
votes
3answers
520 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: ...
8
votes
1answer
262 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 ...
16
votes
6answers
2k 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 ...
8
votes
1answer
390 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 ...
4
votes
2answers
2k views

Function returning Null along with other unexpected expressions

When I use some function, at the end along with the output I get some NULLs returned that I don't understand the reason for and are highly undesirable. For example, when I define the reversal of list ...
31
votes
2answers
924 views

Is there a name for #1@#2&?

Why does the pure function # @ #2 & have no name? I'm asking because sometimes I find inelegant to write expressions like ...
14
votes
1answer
415 views

How do I create a triangulated surface from points?

I have a set of points in a nx3 matrix and I would like to convert them into a surface, so that I may calculate its surface area. The function ListSurfacePlot3D creates the surface how I want it. ...
27
votes
2answers
618 views

Why is Query so much slower than Part?

Time for another of these(1),(2) as yet another new-in-10 function appears to have poor performance compared to older alternatives. This time: Query appears to be ...
13
votes
3answers
571 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 ...
9
votes
4answers
1k views

How make f[{x,y}] evaluate as f[x,y]? [duplicate]

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 ...
6
votes
4answers
794 views

Function argument to default under certain condition

Inspired by this and this question (and how I handle this in practice), what is the best way to default a function value when a certain condition is met? For example, if a function is defined as: ...
4
votes
3answers
894 views

Simplify function notation

I have some calculations with arbitrary functions. In the output, Mathematica always shows the functions with its arguments. I would like to tidy the notation a bit, by hiding the arguments in the ...
19
votes
2answers
373 views

Why doesn't a Composition[] hold its arguments and what can be done about it?

Now that Composition (also RightComposition) has shorthand syntax I am more inclined to use it, however what I feel should be ...
7
votes
0answers
86 views

NotebookWrite a Cell with WholeCellGroupOpener option [duplicate]

Why NotebookWrite[ EvaluationNotebook[], Cell["ZZ", "Section", WholeCellGroupOpener -> True] ] produces: ...
10
votes
5answers
404 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 ...
7
votes
4answers
783 views

Solving $L=\frac{3}{2} \sqrt{4 \pi ^2 A^2+W^2}-\frac{\sqrt{5 W \sqrt{4 \pi ^2 A^2+W^2}+6 \pi ^2 A^2+3 W^2}}{\sqrt{2}}+\frac{3 W}{2}$ for $W$

When I solve the aforementioned equation for $W$ or $A$ on Mathematica I get a long and ugly equation in return, namely one of the solutions for $W$ is: (attempt to read at your own health) ...
13
votes
6answers
1k 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 ...
11
votes
2answers
580 views

Nest , Fold … is there an extension for more than 2 arguments?

Fold is an extension of Nest for 2 arguments. How does one extend this concept to multiple arguments. Here is a trivial example: ...
11
votes
3answers
645 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
1answer
171 views

why Level does not sort output according to their levels

Consider this example: Level[a + f[x, y^n], {0, Infinity}] (*{a, x, y, n, y^n, f[x, y^n], a + f[x, y^n]}*) Why the output is sorted in this way. why not ...
6
votes
5answers
284 views

How to nest my own “times” function to get powers

I have a "times" function. I'd like to create a power function using it. It should look like this for an 6th power: ...
44
votes
3answers
583 views

What bug fixes can be implemented in init.m?

In comments on this question, Mr. Wizard suggested a community wiki to share the bug fixes/workarounds (or possibly other tricks) people load in their init.m. I ...
25
votes
1answer
559 views

What are SparseArray Properties? How and when should they be used?

A strange undocumented form of SparseArray is increasingly used in answers on this site: ...
25
votes
2answers
30k 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 ...
20
votes
5answers
5k views

How can I differentiate numerically?

Mathematica has two ways to integrate: Integrate and NIntegrate. But what about D? ...
25
votes
0answers
556 views

Performance problems in new Sequence functions

The new-in-10.1 Sequence* family of functions should provide newly optimized methods for handling sequence problems. Happily in some cases they do! For example ...
20
votes
1answer
224 views

How to get Cases to wrap results in an arbitrary head?

A number of functions provide for results to be wrapped in an arbitrary head. This is very important in cases where the results should not be evaluated. Take ...
17
votes
1answer
2k 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 ...
16
votes
1answer
360 views

GeoGraphics: problem with GeoPosition in shifted projections

Bug introduced in 10.0.0 and persisting through 10.4.1 A remark about the answer: My work around is only nice for simple cases with points. More general should include proper polygons splitting on ...