# All Questions

402 views

### Can SetDelayed (:=) be compiled?

Is it possible to put an If statement as below within a compile (see below)? I received a warning about SetDelayed. ...
1k views

### Embed CDF into an Apple iBook?

Edit From the comments I received and verifying the information about CDF at wolfram.com, it appears that it is presently impossible to embed CDF into iBooks. WRI does not appear to be happy with this ...
202 views

### Setting a lower limit on calculation time

Sometimes it can come in handy to set a lower limit for a calculation. Consider for example an animation that is generated by some infinite loop, which would run way too fast to display properly for ...
926 views

### MaxSteps and Computing time issue for Solving Differential equation in Mathematica

When we solve differential equation numerically using NDSolve then sometimes we get error like NDSolve::mxst: Maximum steps reached According to Mathematica docs ...
88 views

### Separating exponential terms

Suppose I have a lot of expressions multiplied by factors such as: $$e^{-i\theta[1]-i\theta[2] - i\theta[3]-i\theta[4]-i\theta[5]}$$ I would like to separate this into a product of exponentials of ...
132 views

What I did: ...
192 views

### Can't run bash scripts from within Mathematica 10.1

I am working on Debian 8 and Mathematica 10.1 (64-bit) Home Edition. I have created a script named curl_fetch.sh It contains the line : curl www.google.com > html.txt Running ./curl_fetch.sh on a ...
69 views

### Faster use of Condition for a large array (see the example)

Here is the example/problem. I have a array of $n$ random number. n = 2000; p = RandomReal[{0, 9}, n]; I have to create a $n\times n$ sparse matrix with ...
161 views

### How to assign symbols to functions

Several functions work with symbols in MMA: Take for example Part: l1=l2=Range[4]; l1[[3]] (*3*) l2[[4]] (*4*) I want to make ...
174 views

### Adding noise to nonlinear ODE system

I have a problem with adding a noise to 3d order ODE nonlinear system. I solved the system numericaly and got the periodic solution and now I need to add random pertubations. Due to the lack of ...
105 views

### How to simplify exponents of the form $\exp\left(i\frac{2\pi}{N}(N+1)\right)$ inside a function

I'm really annoyed with Mathematica and I need your help. I defined a discrete Fourier-Transformation(I use II instead of N, because Mathematica wont let me-.-): ...
135 views

### Evaluation of Derivative in a Module

Can someone help me understand the evaluation procedure in the following two pieces of code? ...
91 views

### Why is the Spherical Bessel Function acting strangely at this point?

I'm doing some computation that requires the use of Spherical Bessel Functions of the 1st kind, at high orders and values. So, I managed to find this, while running it over a wide range of values. I ...
76 views

### Make a time IntervalSlider

I want to make a time interval slider with an initial setting of (10:00:00 Mar. 8 2015, 12:30:00 Mar. 8 2015) and which varies from 00:00:00 Mar. 8 2015 to 22:30:00 Mar. 8 2015 with a granularity of ...
157 views

### Dynamic arrays and lists with compile (Append, Linked lists etc.)

I have a code that I need to compile. The code contains a loop in which I need to gather data into a list. The question is how to best gather data so that the code works inside Compile. The following ...
243 views

### Approximate $h$ in $F(\theta)=\sin \theta \int_{-L}^{+L}h(z)e^{-ikz\cos \theta} \,dz$

Consider $$F(\theta)=\sin \theta \int_{-L}^{+L}h(z)e^{-ikz\cos \theta} \,dz$$ $$|z|\le L$$ $$0 \le \theta \le \pi$$ By having knowledge of $F(\theta)$, how can one approximate $h(z)$? In ...
305 views

### Fullsimplify does not simplify Abs'[1.-a]

I have to simplyfy an expression involving Abs' This works: FullSimplify[Abs'[1 - a], a ∈ Reals] Sign[1 - a] but this ...
504 views

### Import data from first/last 100 rows of a file

If one wants import data from the first three rows of a file "myfile.data", one can use the command Import["myfile.data",{"Data",{1,2,3},All}]; However, if I ...
169 views

### Different between two graph in the Polar Plane

How can I plot $\theta=\cos r$ in polar plane? Of course I know that is different with $r=\cos \theta.$
125 views

### Eigenvectors of large symbolic matrix

I have large symbolic matrix of order 32 x 32 given as ...
197 views

### Trouble with Position[] [duplicate]

I am in trouble with Position, Although my example works as expected it throws a warning. Position[{{a,b},{a,c},{a,b}}, _?(#[[2]]==b&), {1}] During ...
224 views

### Exporting of Animated gif from polar plot

I want to export an animation(gif type) for polar plot $r=\cos 2\theta$ like to the following gif. how can I do it?
242 views

### Plotting a plane using intercepts

I have a plane 2x + 5y + z = 10. I have determined that its intercepts are: x = 5, y = 2, z = 10 I need to use ...
408 views

### How to load a custom mathematica package from a .m file?

I would like to load the package groebner50.m which is available through the website of David A. Cox. It's supposed to contain some useful tools for commutative algebra, but I haven't been able to get ...
134 views

### How to remove recursion, and write it functional and efficient way?

I wish to implement the following recursion efficiently. ...
202 views

### Difference between double quotes

I have a notebook and I enter something like PlotLabel->"my label with dynamic number "<>ToString[strange] and I get errors like However, the double ...
287 views

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### Computing kernels of a matrix in distinct cases

I have the following matrix: ...
138 views

### Change font of formula number in DisplayFormulaNumbered

I am trying to change the font of the formula number in a cell which has style DisplayFormulaNumbered. I can easily change the font of the formula I enter by selecting it and using the format menu. ...
142 views

### Generating function for Newton series?

The function GeneratingFunction gives generating function for Taylor series. Is there a similar function for Newton's series? $$f(x) = \sum_{k=0}^\infty \binom{x}k \Delta^k [f]\left (0\right)$$
149 views

### Expectation of a composite Markov-Gamma distribution

In a model I have a discrete two-state first order Markov process, defined by a (2x2) transition matrix with two free parameters. If the first state occurs then the process outputs zero for that ...
370 views

### How to add periodicity to condition?

Is it possible to set the following function f[a], where a can be any real number?  f(\alpha) = \begin{cases} 1 ...
96 views

810 views

### Select row from a table by column value [duplicate]

I have the following: animals = {{dog, black, 200}, {cat, white, 100}, {moose, brown, 500}, {zebra,black,100}} If this came from a SQL table called animals, ...
891 views

### Intersection of surface with parallel planes

Consider the code (adapted from here) ...
562 views

### More elegant way

I read ReplaceOrRemoveInvalidOrMissingData Mathematica documentation, and I tried to apply the same approach to my dataset. I've got two problems, but one is only a style problem! There is one more ...
554 views

I want to do some large data analysis, and i want to be able to import files in a fast way. I tried Import, but it is quite slow; ReadList takes half the time. This is the code I was using: ...
169 views

### Performance on Multinomial Deviate is slow

Most of the time in my program is spent on this single line of code: out = RandomVariate[MultinomialDistribution[nt, tmp]]; ...
221 views

### Simplify equations with pattern assumptions

When simplifying an expression using Simplify[expr, assumptions], the assumptions has to be explicit. Is it possible to simplify an expression with pattern ...
331 views

### How to do Cases with multiple related patterns?

I would like to write a function similar to Cases, but can search for a group of related patterns together. For example, ...
193 views

### Prevent Mathematica from “romanizing” a string of letters?

When I'm authoring in text style (Alt-7), I'll often include inline math. Whenever I enter two or more consecutive letters (e.g., $ax^2$), Mathematica will automatically "romanize" (or "un-italicize") ...
432 views

### Animation is jerky, but slider is not

When I do the following simple animation (from the book Mathematica Navigator, p. 316) the slider control changes the image smoothly, but when I play the animation it is jerky. Is there anything that ...
363 views

### Assigning an analytical approximation to the error function erf(x)

Working with some iterative integral equations, I have Gaussian density functions involved therein. Integrating the Gaussian function I obtain the error function. When I take the second integration, ...
I want to write recursive function for calculating the arithmetic mean of a vector. For $X(n)=\{1,2,3,\ldots, n\}$, the formula is ${\rm Mean}(X(n))=((n-1)\, {\rm Mean}((X(n-1))+X_n)/n$. My ...