# Tagged Questions

Questions about how Mathematica evaluates expressions, tracing evaluation (Trace*), handling expressions in unevaluated form (Hold*, Unevaluated), nonstandard evaluation, etc.

128 views

### Defining a function that prints both the name and value of a variable defined locally within the calling function

To save time when debugging with Print statements, I'd like to define a function -- call it PrintVal -- that prints both the name and value of a variable defined locally within the calling function. ...
347 views

### Why does the documentation call functions “pure”?

Clearly, functions in mathematica are not pure functions according to the definition on Wikipedia (no side effects - basically implementabe with table lookups): ...
68 views

### Is there a simple function identify the sign of an expression given constraints

I'm looking to find a simple function that can identify the sign of an expression given a set of constraints. I have looked around and do see that there is a few threads on this but I'm not sure I ...
51 views

### How can I get numerical answers to integrals involving the error function?

This is the integral I am trying to evaluate in mathematica: Integrate[Exp[-p^2/(m w h)], {p, -Infinity, Sqrt[h m w]}] Can someone show me how to get a numerical answer out of this?
90 views

### Assigning to the “local” version of a symbol

Compare Manipulate[c[1] = 1; c[1], {c[1], 0, 1}] with Manipulate[Do[c[i] = 1, {i, 1}]; c[1], {c[1], 0, 1}] The first case ...
790 views

### DSolve cannot solve for certain branches of the solution

Update - This has been fixed in 10.0.0 Could somebody please tell me, why I am always getting an error message when trying to run the following code: ...
71 views

### A problem about sorting final result

Three days ago, I asked a question about B-Spline Basis fuction here @Michael E2 given a solution to make the order of interval looks normal The easiest way would be to sort it afterwards: MapAt[...
3k views

### Keyboard shortcut to evaluate notebook

(If this is entirely trivial, although I couldn't find an answer as much as I searched the archives, I will delete the question.) How could I add a keyboard shortcut to evaluate the entire notebook ...
455 views

### Prevent graphics render inside held expression

Assuming each odd line is input I would like the even lines to be the output of the following lines. In the above the Graphics are inside ...
98 views

### How can I set a RadioButton to invoke an action, like a Button can?

In Mathematica one can create a Button which, when clicked, invokes an action. For example... ...
159 views

### Tracking Initialization

How to track Initialization step by step? Any tricky solution is ok. One condition, x should be ...
693 views

### HoldForm doesn't hold form

Bug introduced in 10.0.0 and fixed in 10.0.1 In Mathematica version 10, HoldForm no longer produces the same results as in version 8 (edit: I only have versions ...
165 views

### Strange Behavior when making Equal Listable in Pick

While trying to make this problem more efficient I tried different methods and dabbled with making Greater and Equal ...
138 views

### Showing “updating…” message while Manipulate is re-evaluating

Is it possible to show a fixed text such as "updating..." instead of the last result shown, when Manipulate is re-evaluating an expression (in a slow evaluation ...
328 views

### Return partial result when MemoryConstrained aborts NDSolve

I use NDSolve to solve a large set (~400) of coupled ODEs. Sometimes, the memory (~4GB) gets filled up, and my computer becomes impossible to work with, because it ...
297 views

### Menu item “Interrupt Evaluation…” missing in V10

The menu item “Interrupt Evaluation…” seems to have disappeared in Mathematica 10 on OS X. Well, this is a bummer. I personally use Mathematica for very long calculations, and I was using this ...
78 views

### Inactive derivative: extract constants

I have a problem with an unevaluated derivative. In the example code below, i need the integration wrt to y be evaluated, while the differentation wrt x needs to stay unevaluated. I see the point that ...
283 views

### difficulty abstracting the OptionValue pattern

I am building lots of functions that use Options and OptionValue and wanted to reduce the redundancy in the expressions that ...
46 views

### Ivar error with Fit inside Plot

I'm trying to plot this Plot[Fit[med,{1,x},x],{x,0,10}] Why this doesn't work? I find out that if I do ...
219 views

### Algebraic expressions on pure functions

I would like to know how to perform algebraic operations with pure functions. Simple version: Here's a silly toy model: I want to transform the algebraic expression Sin*Cos into the function ...
296 views

### Functional-Style Partial Application and the Accumulator Pattern?

Following up on Functional-style Fixed-Length Queue Object?, I want to generalize it to a functional-style accumulator pattern. Lots of things look like accumulators, loosely defined as binary ...
126 views

### Side-effecting an array in an association?

I'm working on some classical data structures (stack, queue, etc.) and want to mimic oo style in MMA. As a first attempt, I want to store an array in an Association, like this: ...
110 views

### How to explain the behavior of Rule inside these functions [duplicate]

I'm trying to define a function that takes an expression and spits out a pure function involving a replacement rule of that function's variable. An example would be a function ...
546 views

### kernel Local crashes during the course of a For loop

I want to find the minimum of the function r[x,p] subject to the constraint w[x,p,t]==0 (t ...
198 views

### Can $\it{every}$ usage of While be changed into NestWhile?

Ok, I think this problem is more close to philosophy. :P I've some idea now. But I'm not sure whether it's correct. For the purpose of convenience, I will use some C-like code instead of MMA's. A <...
81 views

### Mathematica automaticly evaluates some cells

Is there a command or a trick to tell Mathematica to not automaticly evaluate some cells? I use the NMinimize function to calculates some coordinates and then use ...
177 views

### Memory problem in Mathematica 10

I'm having a problem with memory. I'm doing nonliner fits of several data lists to a system of differential equations. When I evaluate the "Do" cycle the memory grows with the iteration step up to my ...
75 views

### Evaluation inside Compile

here's a simple question: I have a function: ...
307 views

### How to simplify expression and use HoldForm at the same time?

Hopefully a simple problem for the experts here. I have a need many times to build a symbolic expression for an equation (say a PDE) to use for plot labels in a low level function inside ...
222 views

### Why does Mathematica appear to change the head of certain expressions?

I don't know if the question trivial or not (if so I will delete it), but here is what I have: I know that x x (* x^2 *) Looking at the full form gives <...
179 views

### Simplifying a symbolic product of rational powers

I'm trying to symbolically evaluate a lot of equations that can consist of up to 10 parameters. The form of these expressions is a product/quotient of rational powers of the mentioned parameters, ...
33 views

### Expressions to functions, and evaluation [duplicate]

When calculating derivatives a expression is the result: in:= f[x_,y_]:= 1 + 2 x + 3 x^2 y + 4 x y^2 in:= D[f[x,y],x] out= 2 + 6 x y + 4 y^2 how do i make this ...
87 views

### Order of Evaluate for Map

I would like to get a list of variable names as strings. For example, x = 1; y = 2; Map[SymbolName, Unevaluated /@ Unevaluated@{x, y}] {"x", "y"} This works ...
252 views

### How to make a table of $\sum_{i=1}^n$?

I want to create a table of $\displaystyle \sum_{i=1}^n i^k$ for $1\le k\le 5$. The output I want to obtain is a TeXForm output as follows. \begin{align} \sum_{i=...
133 views

### Example from Mathematica documentation (ExtremeValueDistribution) seems to be evualting “forever”

I am referring to this example at the reference page for the extreme value distribution: http://reference.wolfram.com/mathematica/ref/ExtremeValueDistribution.html#6764486 The first three commands ...
80 views

### With command does not behave as expected according to its Attributes

The attributes of the With command are HoldAll which means it should not evaluate its arguments before its starts its business. ...
54 views

### Timing of ParallelDo versus Do: simple example [duplicate]

I'm trying to understand why a simple do-loop takes substantially longer when done in parallel than sequentially: ...
165 views

I'm trying to build an ExampleData browser, so that the "collection"/"type" is selectable in a drop down menu, and the "name" is selectable in another drop down menu. What I have so far: ...
362 views

### Performance of Dispatch and lists of Rules

The issue outlined here seems to be no longer present in version 10, if you use a Dispatch table! This because a Dispatch table ...
133 views

### Pattern matching to head with HoldFirst

I want to define a function that only operates on expressions with a head from a given list, such as f[expr:(_And|_Or)] := Print["LHS is ", expr[[1]]]; This of ...
276 views

### How to get the absolute difference between two angles

I need a function that will give me the shortest separation between angles that range from -pi to pi. For example if I have two angles 3pi/4 and -3pi/4, I would like a function that will tell me pi/2 ...
152 views

### Generate conditions seems to not work [closed]

I am trying to compute the following integral Integrate[E^(I*k*Omega*t), {t,0,T}, GenerateConditions->True] for which Mathematica returns ...
839 views

### Why are functions called first-class objects in Mathematica?

I've heard lots of people say a function is a first-class object in Mathematica. "Everything is an expression, including function." "There is no distinction between functions and data." Having read ...
82 views

### How to implement nested With as a single construct using functional programming (Fold)?

It is possible to define my own With construct where each local constant can depend on the previous defined local constants? I wish to replace something like this ...
375 views

### FindRoot with vector functions

I'm trying to solve a system of non-linear equations with FindRoot, and I get the answer, but also a ...
416 views

### How does Mathematica interpret a expression?

I'm a beginner to Mathematica. I'd read several document. But I still have a problem. For example, every expression in Mathematica are of the form ...
175 views

### ParallelEvaluate: Evaluation Rules and Increment

I'm trying to understand how ParallelEvaluate works, considering the two following snippets: ...
410 views

### Automatically evaluate next cell

I am new to Mathematica. I am trying to achieve the following: I need one input cell in which I set parameters, then another input cell where functions are defined and calculations are performed. ...