Questions about how Mathematica evaluates expressions, tracing evaluation (Trace*), handling expressions in unevaluated form (Hold*, Unevaluated), nonstandard evaluation, etc.
2
votes
2answers
103 views
How to make Mathematica returns the exact expression I typed
I'm using Mathematica to compare some constants. Before playing around with those constants, I would like to check that I didn't make any mistake in typing them. So my question is the following: "What ...
1
vote
1answer
91 views
Evaluate code to some point
How can I evaluate my code, up to some point? I don't want to evaluate all of my code always.
I have to use Shift - Enter for every line from the first cell up to the point I want to be, and it's not ...
8
votes
4answers
149 views
How to pass a list of arguments into HoldAll
I have a list of arguments (which in reality is lengthy):
arguments = {a, b, c}
arguments2 = {a_, b_, c_}
f[Sequence@@arguments2] := a + b + c
Note: It seems ...
4
votes
4answers
205 views
Efficiently finding the positions of a large list of targets in another, even larger list
I have a big list. It contains nearly 60,000 sub-lists. It's structured like
bigList= {{x1,y1,z1},{x2,y2,z2},{x3,y3,z3},.....,{x60000,y60000,z60000}};
...
0
votes
0answers
22 views
Define a Plot3D function with custom options [duplicate]
I am trying to define a Plot3D function with custom options, following (this previous SE question), but I'm running into a brick wall. I've narrowed the problem to the following 'toy' code:
...
11
votes
1answer
321 views
Get the current iteration count
I would like to be able to get the current iteration count, the one that if exceeds $IterationLimit makes the evaluation stop.
After not finding a magical variable ...
1
vote
0answers
39 views
Confusing efficiency and evaluation when returning pure functions? [duplicate]
I have a function that takes some time to evaluate, that's meant to be a polynomial approximation to a function. The polynomial is defined by a list of coefficients, so I have the function ...
10
votes
4answers
152 views
How do I evaluate the terms in an expression, but not the expression itself?
I am trying to write a set of homework questions.
I would like the output to evaluate the constants but not the sum, so that I may present the homework question as something like this:
...
5
votes
4answers
204 views
Prevent Part[] from trying to extract parts of symbolic expressions
If you have a list, e.g.
{1, 2, 3}
then you can extract the $k$th part using Part (...
0
votes
0answers
31 views
Finding solutions based on set criteria [duplicate]
If anyone would be so kind, I'm wondering if I could get a basic direction in Mathematica to begin coding a method for taking a set of resources (numbers and operators) along with a set goal/answer, ...
0
votes
1answer
91 views
NumericQ prevents evaluation at a numerical value sometimes
I set up a symbolic integral, to be evaluated only when some of the symbols have been replaced by numbers. The evaluation after assigning numbers to the symbols is still symbolic for some reason. The ...
4
votes
1answer
95 views
Identical code, different answers?
I'm having some trouble with identical code giving different answers. On a fresh kernel (MM 9.0.0.0, Windows 64-bit), running the same code, copy-paste, gives two different answers:
...
0
votes
1answer
97 views
Why won't ContourPlot accept a variable argument? [duplicate]
I have a list of linear inequalities which describe a (polygonal) region. I can use RegionPlot to visualize this region; but I'd also like to overlay this plot with ...
4
votes
3answers
143 views
Keep function range as a variable
Plot[2*x^2 - x + 2, {x, -1, 1}] plots a function of x from -1 to 1. As far as I can see, I cannot "save" this range in a variable:
...
3
votes
1answer
57 views
Stop TradtionalForm evaluating expression
I'm trying to get this expression to display as typed instead of evaluating the 1/1.121.
...
1
vote
1answer
108 views
Forcing evaluation of ArgMax
How to force evaluation of ArgMax before its output gets used in Solve?
Background: I'm trying to solve for the Nash ...
2
votes
1answer
106 views
3
votes
1answer
232 views
How is the Mathematica kernel structured internally, and how does evaluation work?
There is so much information available for Java--the internal details of (for example) the JVM memory manager are well-documented, and the performance considerations arising from its interaction with ...
3
votes
0answers
190 views
A is fast, B is fast, but together they're Mathematica-crashing slow?
I'm trying to do something with finding solutions to a quantum mechanics problem with n wells. If there are 40 wells, I need to find the solution to an equation in the form:
...
4
votes
1answer
168 views
Behavior of expression evaluation in Plot
I'm confused with Mathematica's way of parsing expressions. I've been struggling with this for a while and never found an exhaustive answer, sometimes things don't parse the way I think they would ...
23
votes
2answers
688 views
Block attributes of Equal
I answered “Equating matrices (or higher order tensors) element-wise” with:
...
4
votes
1answer
119 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 ...
5
votes
1answer
133 views
Strange Behavior with RegionPlot
Consider the following code.
RegionPlot[Print[{x, y}], {x, -2, 2}, {y, -2, 2}, PlotPoints -> 2]
...
2
votes
0answers
89 views
Strange double evaluation using MorphologicalGraph
(MMA 9.0.0 on Mac OS/X 10.8)
Please consider the following snippet (this is as SMALL as I could make it -- my attempts at making a smaller repro-case eliminated the effect that I am investigating)
...
12
votes
1answer
107 views
Exclude Sections/Subsections/… from evaluation
I'm working on a large notebook and I want to exclude some sections and subsections from being evaluated when I evaluate the whole notebook.
Is there a way to exclude specific sections or ...
1
vote
1answer
116 views
Summation of If statements
The following made me curious. Suppose you want to sum the if statement If[x[i] < 1., x[i]^2, 0.] over i=1,2, i.e.
...
3
votes
1answer
71 views
Evaluation order of Button[]'s action
it looks like it should be well known issue but I haven't found answer anywhere.
Please tell me why the result (after clicking) of this:
...
12
votes
1answer
227 views
Using Evaluate and Evaluated -> True in Plot
A few use cases:
(1) This, as expected, returns (almost) immediately:
f[x_?NumericQ] := Evaluate[(Pause[1]; x)]
Plot[f[x], {x, 0, 1}]
(2) This takes ...
0
votes
2answers
148 views
How can I get the approximate analytical solution to this simple algebra equation?
Is there a way to get the analytical form to the root of this equation
2 A e (-ArcTanh[smax/s0] + ArcTanh[(smax Cos[w \[Zeta]])/s0]) == F0
...
1
vote
2answers
279 views
Derivative of a spline approximation
To approximate an experimental data function $f(t)$ with $t \in (t_{min},t_{max})$ I used a cubic spline $s(p)=(t(p),f(p))$ with the parameter $p \in (0,1)$ and $p = t/(t_{max}-t_{min})$ by using the ...
3
votes
1answer
178 views
Log function - why is Log[b,b] not being evaluated to 1?
Have been experimenting with the Log function to demonstrate simple Log relationships such as Log[xy], Log[x+y] etc.
...
5
votes
1answer
96 views
Why does this pattern with Plus not work for numbers?
I have a very simple question about redefining basic built-in functions, such as Plus. I'm pretty sure someone must have asked a similar question around here, but I ...
3
votes
2answers
82 views
UpValues evaluation with Dot operator
I would like to simplify some database notation, and I'm doing some tests with UpValues for that.
For example, if I set this Upvalue fot tab1:
...
0
votes
1answer
166 views
Make Mathematica wait before replacing?
How can I force Mathematica to completely evaluate a subexpression before using a replacement rule?
For example, consider the following definition (for the series of ...
5
votes
1answer
75 views
how to print stack trace when TimeConstrained times out
According to the documentation, TimeConstrained generates an interrupt which interrupts the computation. This interrupt is treated just like an abort, at least in ...
18
votes
2answers
188 views
Evaluation of OptionValue[]
I have a function that takes an OptionsPattern and I want to access several options, say a, and ...
0
votes
1answer
102 views
Array of functions, evaluation in plot
I would like to create two arrays of functions yfunc[[i]] and tfunc[[i]], with each entry of those functions being a function ...
8
votes
1answer
95 views
How to catch the “Preemptive” evaluations from within the main loop?
When trying to make an optimized version of my plotRange fonction I faced a problem of catching the "Preemptive" evaluations ...
4
votes
0answers
47 views
Problem with inequality using refine
I am using inequalities to follow some line of reasoning in Mathematica and I came across a problem I can not explain to myself. Does from a>=0 and b>=0 not follow a+b >= 0? How does Mathematica ...
7
votes
4answers
157 views
Button's command is not evaluated in iteration
I wish I didn't feel like a newbie after several months, but...
If I enter the following:
Table[ Button[ "Number: " <> ToString @ i, Print @ i], {i, 1, 5}]
...
5
votes
2answers
188 views
Problem with ParametricPlot of multiple Curves
I have written a function f[Ne,t,T], that gives back a list of results when evaluated with numeric values of the variables Ne, ...
0
votes
0answers
46 views
How to ContourPlot a Table? [duplicate]
Possible Duplicate:
Why is ContourPlot not displaying this curve?
Why do I have to put Evaluate[] here
I'm trying to plot certain contours of a function $f:\mathbb R^2\to\mathbb R$.
What I ...
2
votes
3answers
121 views
Function to preserve evaluation on display?
I'm looking for a function that applies the following behavior to an expression:
-When the expression is given as the full input, or as part of a function that cannot be evaluated, it remains in ...
1
vote
2answers
132 views
Why does Evaluate[a[[1]]]=0 assign a value to a variable while a[[1]]=0 doesn't?
I'm trying to do a small page counter with Mathematica, for leting me know about my reading progress on some books. I'm stuck on a problem:
...
4
votes
1answer
139 views
Why does Dynamic output cause CPU usage when onscreen?
I write such a line in Mathematica:
{Slider[Dynamic[s]], Dynamic[f[x_] := s*x]}
After evaluation, the CPU immediately runs at full power. And if you scroll the ...
6
votes
1answer
124 views
PlotStyle does not work when plotting a non-evaluated list of functions
When a list of functions is passed to Plot in an unevaluated form (e.g. with Through), the result is a plot with single color.
...
12
votes
2answers
323 views
Preventing Numerical value from being evaluated
I have searched stackoverflow (and comparable pages) for quite a while now (got redirected from there to this specialized stack), and I surrender. I am trying to evaluate an expression that is small ...
4
votes
2answers
134 views
9
votes
1answer
68 views
Different behaviour of ValueQ inside and outside of a loop
I need to store a rather big number of variables and I tried to do that by storing each variable as Z[n] with varying n. I guess this was not my best idea. The first problem I encountered is when I ...
0
votes
0answers
96 views
Do Import and Get work asynchronously? Can I prevent this?
I'm getting strange behavior in some of my notebooks that makes it seem like Import and Get load asynchronously. When I evaluate ...
