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

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6
votes
1answer
73 views

How to reset the $ModuleNumber?

According to the documentation, we can reset $ModuleNumber to a positive machine integer. There is even an example in the doc: ...
3
votes
1answer
423 views

Order of operations, precedence in Mathematica [duplicate]

I get confused in the order of operations in Mathematica. For example, f /@ 10^{1, 2, 3} {10, 100, 1000} In my head, that ...
0
votes
1answer
99 views

Not evaluating all cells unless I explicitly evaluate each one?

I'm running a Mathematica (version 8) notebook. In one of the first few cells, it is supposed to plot some data. It uses a couple functions that are defined in an above cell. If I do Evaluation-> ...
3
votes
2answers
85 views

Confused with HoldForm in Postfix notation

Why does the following code produce different result? In my mental model, they should be the same. ...
2
votes
1answer
118 views

Strange results of definitions using OwnValues

I am asking this question simultatenously with this one, which is strongly related. I was trying to see if I could create the behaviour as in that question without using ...
4
votes
4answers
718 views
4
votes
1answer
134 views

How can I test properties of a symbol without unwanted evaluation

Problem How to get the head, size, dimensions, etc. of a symbol without evaluating it? Since Mathematica does not allocate fix storage space and type to symbols it is not trivial to query runtime ...
1
vote
1answer
231 views

Skip one step of the loop if there is an NIntegrate::eincr message

Is there a possibility of skipping one step of a loop if in this step there appears an error like NIntegrate::eincr? After skipping, the loop should go to the next ...
0
votes
2answers
841 views

Defining a function in terms of matrix elements

Currently trying to use elements from a matrix in defining a function however having some trouble. This is a somewhat simplified version of the problem. Say I have the matrix ...
15
votes
2answers
952 views

Why do certain values in ArcSin not fully evaluate?

This is a continuation of: Why do certain fractional values in TriangleWave not evaluate? The analysis by R.M and rasher revealed that problem to reduce to the behavior of: ...
3
votes
2answers
148 views

Evaluate in Plot leads to function error

Please help - I'm really struggling to understand why this evaluates with errors. ...
0
votes
0answers
15 views

Evaluating a String that is a Variable [duplicate]

I have a Variable assigned a value, say ImportantDocuments=1 How do I make N["ImportantDocuments"] evaluate to be 1 instead of ImportantDocuments I found that ...
8
votes
2answers
327 views

Understanding Villegas-Gayley

Temporary message: I have written another question about the behaviour the code by Oleksandr R. . Sadly I clicked "discard" and that was lost. I am a bit demotivated now and in order to not let the ...
3
votes
1answer
110 views

Why is held expression evaluated?

Context: I'm studying non-linear dynamics. As part of a bigger problem, I'd like to generate lists of the form {{deq, ic1}, {deq, ic2}, ...}, where ...
4
votes
0answers
204 views

DynamicModule, SaveDefinitions and global functions

Unfortunately, I had not checked stackoverflow, because there, the exact same behavior was already reported. Please see the Q&A "SaveDefinitions considered dangerous". Up-front, I'm on Ubuntu ...
5
votes
1answer
307 views

Evaluation order control

This question is related to Evaluation order of Button[]'s action Concusion was, Button[]'s actions are evaluated in preemptive link so "the code that needs ...
2
votes
1answer
160 views

Piecewise function with user-input interval

I would like define a function g[data,bins,x] which is a piecewise constant function taking value data[[i]] in the range ...
2
votes
1answer
136 views

Need help looping a notebook evaluation

I'm a new user and would like to find the minimum value of soln1[30] obtained after repeating the following evaluation (below) for 1000 cycles (for instance). I can obtain sequential values of ...
3
votes
2answers
127 views

Keep data in memory inside a notebook without having to evaluate it again [duplicate]

I have a notebook that calculates some data in a relatively large time so I want to keep these data saved inside the notebook without recalculate them every time I open the notebook. I know I can ...
0
votes
3answers
87 views

Preventing evaluation until all undefined symbols are resolved

FixedPoint[If[# <= 0, 0, # - 1]&, 2 x] Causes an infinite loop because of 'x'. How do i automatically prevent evaluation until ...
2
votes
1answer
82 views

Need to run evaluation 2 times

Why does this only work after running the evaluation 2 times? ...
2
votes
1answer
109 views

Manual CellGrouping option causes crash at cell evaluation

Update: Try to reproduce this behaviour with CellGrouping set to manual. To do that: either evaluate ...
10
votes
1answer
114 views

Aborting from inside a ScheduledTask

If you have an Abort[] inside a ScheduledTask expression, what does it abort? The scheduled task evaluation, or any main kernel ...
2
votes
1answer
72 views

Evaluate only one from a set of procedures

Let's say I've got a list of procedures: {Print[1];, Print[2];, Print[3];} And I want to only evaluate 3rd one: ...
3
votes
3answers
130 views

Using a variable to tell Mathematica which existing variable to manipulate

I have an estimation routine I have coded up, I want now to do some tests on it where I pick a particular parameter and run the estimation for differing values of that parameter. What I want is to be ...
3
votes
2answers
166 views

Assigning an equation as a variable

I am compiling a calculator where many slider parameters are used to define a value, where the defined value may then be reused to define another value. I am unable able to, or at least been ...
2
votes
1answer
122 views

Differentiating a function that has NIntegrate within it

I am something of a novice with Mathematica. I have written the following code; ...
0
votes
1answer
118 views

Solving NLODE with substitution

I am trying to get a solution to a non-linear ODE, below is the code that works for my problem. ...
10
votes
1answer
225 views

TimeConstrained dynamic change of maximum time

I would like to run a time consuming function: TimeConstrained[f[x],maxseconds] and be able to change maxseconds during running (increasing or decreasing max ...
11
votes
3answers
204 views

Creating a custom context with a Hold construct

I'm trying to create a function "InContext" to execute a piece of code inside a certain context (and to return the result of evaluating that piece of code). One approach is to place the code inside a ...
2
votes
3answers
429 views

GraphPlot only working when I evaluate twice

I have some code that builds a graph and some vertex coordinates, but when I evaluate it I get a message that the list of coordinates is not valid and the graph is not valid and it shows the output as ...
5
votes
2answers
192 views

Remove versus ClearAll

What is the difference between Remove and ClearAll? I thought that "not being recognized by Mathematica", which is the effect ...
2
votes
3answers
143 views

Dynamic plot with Evaluate on expression

I'm trying to make a make a plot of a table of expressions, which should be pre-evaluated (since they are infinite series with analytic sums). I'm able to make the plot normally with ...
1
vote
1answer
120 views

Caching data in Mathematica package

Consider the following: m=Quantity[1,"meter"] If I run the package, it will return 1m But when I load the package, the ...
12
votes
3answers
228 views

Selective evaluation of blocks of code in a Manipulate

Is it possible to attach certain pieces of code to certain controls in a Manipulate? For example, consider the following Manipulate ...
19
votes
1answer
498 views
0
votes
1answer
162 views

Plot[ D[Sin[x]] ] and Evaluate[] [duplicate]

Why does t = 2 Pi; Plot[D[Sin[x],x], {x,0,t}] (* Plotting the derivative of Sin[x] *) not work, but ...
1
vote
1answer
126 views

Printing intermediate calculations in an external file, while suppressing the output in the notebook

I'm trying to construct a text-file that contains all the operations that Mathematica performs when evaluating an expression. However, i'd like to suppress all output in the notebook in which I'm ...
7
votes
3answers
233 views

Why does Mathematica not seem to know that $i^x$ cannot be equal to $0$?

I am experiencing a curious behaviour of Simplify when handling expressions involving powers of $\mathbf{i}$, such as $\mathbf{i}^x$ where $x$ is unknown. For ...
1
vote
1answer
177 views

Passing a joined list of symbols for Module or Block to treat as its own local symbols

The Question I'd like to write a function which itself takes a list of symbols, e.g. Foo[{x, y, z}] to pass to Module ...
4
votes
1answer
533 views
0
votes
1answer
89 views

Plot producing many error messages when given complicated function

I'm new to Mathematica and am running in to all sorts of silly difficulties with coding in it. I'm trying to calculate a function f[x, k], normalise it with another ...
2
votes
1answer
250 views

Why is this expression being held, and how can I evaluate it?

I can't figure out why an expression isn't evaluating, even though there's no Hold* in its FullForm: ...
11
votes
4answers
332 views

Using With to scope over pure functions

Consider this example: given an option for a function func as "x" :> (a&), how can one assign different values to ...
1
vote
1answer
42 views

Output cell written with NotebookWrite dissappears on whole notebook evaluation, yet remains if I individually evaluate it

Create a new notebook with the following two input cells: NotebookWrite[EvaluationNotebook[], Cell[BoxData[ToBoxes[Manipulator[Dynamic[x]]]], "Output"]] and ...
0
votes
1answer
86 views

Evaluate outer function first

I'm new in Mathematica so this is maybe super easy to do, but I can't figure out how. I've got a function plus[a,b] that sums two numbers and I need to implement a ...