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

learn more… | top users | synonyms

0
votes
1answer
299 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 ...
0
votes
1answer
329 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 ...
0
votes
1answer
69 views

How can I restrict a notebook to evaluate only if I am user 'root'?

I am playing with openCL on Linux with an AMD gpu, and due to a glitch in the driver, I need to be 'root' to get stuff to work. Installation question here.
0
votes
1answer
147 views

Slow Dynamic Button Does Not Print [duplicate]

Possible Duplicate: Why do buttons with ChoiceDialog freeze the front end? Why is SystemDialogInput failing to return a save file path? Evaluation inside Button stops after some seconds I ...
0
votes
1answer
58 views

How do you stop Mathematica from evaluating a sum? [closed]

A concentration $A(i,j)$ varies over i,j. I'd like to include the summation of $A(i,j)$ in my Mathematica expressions, but it evaluates the sum ...
0
votes
2answers
45 views

Parallel evaluation hangs before doing anything

[I use Mathematica 9.0.1.0 on OS X Yosemite 10.10.2.] I am experiencing difficulty with parallel evaluation that I am finding extremely perplexing to troubleshoot. I define the following function in ...
0
votes
1answer
101 views

How to make Mathematica show intermediate steps in integral [duplicate]

I want to know how Mathematica evaluates this integral: $PV \int _ {0} ^ {i \infty} d \tau \, \frac{e^{-\frac{\tau^2}{2 M^2}}(b^2 - 3 τ^2)^2 (|b^2+\tau^2|-(b^2-\tau^2))}{\tau (\tau^2 - b^2)}$, where ...
0
votes
1answer
45 views

Why returning False? [closed]

Can anyone explain the false? I'm trying to grab co-efficient in front of X^2 I think. I say I think as I'm following my tutors example using his screenshot the only difference between his question ...
0
votes
2answers
58 views

Failed to use N[%] for a infinite series

I am trying to evaluate a infinite series: $$ 2 \sum _{l=1}^{\infty } \Re\left(n^{\frac{2 i \pi l}{\log (q)}} \Gamma \left(\alpha -\frac{2 i l \pi }{\log (q)}\right)\right) $$ With the code: ...
0
votes
1answer
52 views

Unknown Power showing up in Formula [closed]

I have the following worksheet below. (I took a screen shot because I didn't know how to type the code for the particular function). Circled in red are powers that shouldn't be there and yet ...
0
votes
1answer
60 views

Defining a function with algebraic parameters

I am trying to define and use a function to represent the eigenstates of a Quantum Harmonic Oscillator, which have the general form: $$\psi_{n}(x) = \frac{1}{\sqrt{2^{n} n!}}\left(\frac{m \omega}{2 ...
0
votes
1answer
40 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?
0
votes
1answer
54 views

What's the difference between this differentiation? [closed]

I've tried to evaluate a sum and get a result in terms of Zeta function. And I have results in two forms: ...
0
votes
1answer
114 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, ...
0
votes
1answer
400 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 ...
0
votes
1answer
49 views

Resolving Error: Mathematica evaluation order on Lists

I have a table that is 27 x 27, each entry corresponds to an element from the periodic table. I use the replacement rules in element list to allow me to convert a list of elements into a list of ...
0
votes
1answer
118 views

Symbolic integral including Hermite polynomial does not evaluate

I am trying to evaluate the following integral: Integrate[HermiteH[n, Sqrt[a]* x] * Exp[- (c/2)* (x^2 + y^2) + b* x * y - (a * x^2)/2], {x, - Infinity, Infinity}] ...
0
votes
2answers
273 views

Defining Piecewise Functions in Modules

In short, my question is the same as my previous one except that everything is now wrapped up in a module. The relevant code I'm working with is: ...
0
votes
1answer
142 views
0
votes
2answers
842 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 ...
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. ...
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 ...
0
votes
1answer
140 views

Order of evaluation in nested expression

I am trying to make a function that works as follows: Integrate 1 for all t in the interval $ [0,1] $ such that the first element of function vstar is positive. ...
0
votes
1answer
150 views

Understanding output of multivariable integration

I'm new to Mathematica and I'm trying to integrate this function: ...
0
votes
1answer
359 views

Pull Constants outside of integrals

I would like Mathematica to pull constants outside of an integral: e.g., $\int_0^t f[t] g[s] dt \to g[s] \int_0^t f[t] dt$ This has previously been discussed at replacement rule to pull independent ...
0
votes
0answers
53 views

Preventing Power from evaluating principal value

Can I prevent Power from evaluating the principal value and force it to keep the expressions in the exponential form until the end of all other evaluations? For ...
0
votes
0answers
31 views

Why is DownValues releasing RuleDelayed's hold for Graphics? [duplicate]

I am trying to understand DownValues in regards to the evaluation of its output. Consider this: ...
0
votes
0answers
25 views

What makes items with head `Function` different?

I apologize beforehand for the muddleheadedness of this question. It reflects the fact that I'm trying to interpret outward "behaviors" of Mathematica expressions without having any understanding of ...
0
votes
0answers
23 views

Timing of an Evaluation is not correctly displayed

From: http://reference.wolfram.com/language/howto/DisplayTheTimingOfAnEvaluationInANotebookWindow.html I ran a process that took about two minutes to finish. But the time recorded is only 0.18 ...
0
votes
0answers
30 views

Alter evaluation order when applying scalar multiplication to function

Consider the following program: g = 2f; g[x] (* (2f)[x] *) Is there any way I can change the above expression to have it return ...
0
votes
0answers
73 views

How can I solve this expression?

I'm trying to solve this expression for A, but I'm not sure how. ...
0
votes
0answers
74 views

Calculating the rank of an abstract matrix

I'm trying to compute the rank of a 4x4 matrix with 4 parameters and 2 variables. I tried to calculate its rank under some assumptions on those conditions and I kept getting rank 4. So I did an ...
0
votes
0answers
83 views

How to prevent long evaluation and infinite loops

I'm new to this, so sometimes I accidentally ask Mathematica to do calculations with numbers so big that it can't handle it and it immediately freezes my laptop to the point where there's nothing I ...
0
votes
0answers
59 views

Creating a lazy evaluator of the lambda calculus

I have a sub project in my research to write a lazy evaluator of the lambda calculus. How should I approach this problem? I already have a implementation of the lambda calculus in another language. ...
0
votes
0answers
62 views

subtlety of self-defined function and its evaluation [duplicate]

I wrote a simple code as follows f[x_,y_]:=NIntegrate[x+z,{z,0,1}]; g[x_,y_]:=NIntegrate[y+z,{z,0,1}]; VectorPlot[{f[x,y],g[x,y]},{x,0,1},{y,0,1}] then ...
0
votes
0answers
106 views

How to speed up my code with constructing matrices

I have run this program for a long time to get the result for n = 2048(about 5hours) and no more result till now (can't run with n = 4096). I would know how to make it more efficient. Any help or ...
0
votes
0answers
74 views

Trying to Simplify an Expression

I'm trying to simplify an expression: ...
0
votes
0answers
49 views

Order of evaluation when using Solve and Minimize

I have to solve numerically an integral, that ends up being more or less as follows: Solve[f[x]==a*Sum[Sin[x-i]*(f[i]-f[i-1]),{i,1,x}],f[x]] (not actual ...
0
votes
0answers
52 views

Evaluating Expectation [duplicate]

I would like to have a result equal to a function : ...
0
votes
0answers
31 views

reloading previously evaluated inputs? [duplicate]

How do I avoid having to resend previously evaluated commands when I reopen my notebook? can't it just allow me continue my computation from where I stopped? Also, some inputs take forever to execute, ...
0
votes
0answers
27 views

Expanding Function Based on Congruence Classes

I'm trying to get Mathematica to expand $\quad \quad \beta_n=\sum_{r=0}^{n}\frac{\alpha_r}{(q^4;q^4)_{n-r}(q^4;q^4)_{n+r}},$ where $\alpha_r$ is an integer valued sequence that is given by ...
0
votes
0answers
104 views

Mathematica not evaluating q derivative of Jacobi theta function

Jacobi theta functions, $\theta_a(u,q)$ for $a=1,2,3,4$ are defined in the unit disk $|q|<1$. For some reason that I would like to understand, Mathematica does not evaluate numerically the $q$ ...
0
votes
0answers
55 views
0
votes
0answers
145 views

Mathematica not responding

I am working in the field of applied physics. Some body suggested me to use Mathematica for plotting graphs and programming. After going through some tutorials, I have written the following code but ...
0
votes
0answers
56 views

System of Nonlinear equations with Gamma and Incomplete Gamma function

The next two nonlinear equations are cumulative ratios of a production system. The mathematical model includes two essential parameters (n, tau) that can be obtained by solving this system. I'm ...
0
votes
0answers
77 views

kernel stops evaluation, clears variables

I am using the new Mathematica 10 student edition. As I am evaluating a table of integrals and calling NIntegrate repeatedly, the evaluation stops without error and the kernel clears all variables. ...
0
votes
0answers
49 views

Evaluation inside Compile

here's a simple question: I have a function: ...
0
votes
0answers
31 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 ...
0
votes
0answers
51 views

Scoping problem with Manipulate [duplicate]

Consider the following simple code: f = Sin[a x]; Manipulate[ Plot[f, {x, 0, 10}], {a, 0, 10}] Manipulate takes f to be ...
0
votes
1answer
66 views

Optimizing repeated function calls

Easiest way to keep my library nice, is to naively call some functions many times with same parameters. Doing so prevents from zoo of (library-)global variables and complicated initialisation ...