# All Questions

175 views

### List manipulation - various

Update OK, Please forgive the messiness of this, but I am working with something like: ...
135 views

### Forcing optimal solution for FindShortestTour

I use FindShortestTour as explained here and it works nicely for a small number of cities. However when I try this with as little as 16 cities, the given tour isn't ...
553 views

### Perfect numbers

The question given to me: a. Find the perfect numbers between $1$ and $10^6$ b: Find the abundant numbers between $1$ and $1000$ For a, I wrote ...
163 views

### How to get a list of pairs into the form $(x,y)$?

I want to put the solutions of the equation $y = (x + 3)/(x - 3)$, where $x$, $y$ are integers, into the form $(x,y)$. For example, $(2, -5)$ instead of $\{2,-5\}$. When I evaluated ...
185 views

### How can I make controls have Button-like behaviour?

The Button control is very easy to understand Button["Press Me", Print["Pressed"]] I press the button, I execute the ...
611 views

### Log-log scale smooth histogram

How can I create a smooth histogram with a log-log scale? I can use Histogram[data, "Log", "LogCount"] to get a log-log histogram, or I can use ...
318 views

### Quickly reducing the number of decimal digits for a set of real numbers

How can I quickly convert a number with $n$ decimal points to a number of with $m$ decimal points? Round works, however, it is slower than I would like. This ...
380 views

### Plotting the direction field of a differential equation

I have to sketch the direction field for the following differential equation: $$\frac{dy}{dx}=\frac{-0.02 y +0.00002 xy}{0.08 x-0.001xy}$$ This is the code I used, which gives an incorrect plot: ...
453 views

### Finding central point in a ContourPlot

I am using ContourPlot for defining a 2-parameter space feasibility of a function. This function simply returns 1 if everything is ...
335 views

### How to generalize and speed up this program?

There is a vector whose length is $n*m$, we can part it into $n$ sections in order. I want to define a function to compare the $i$-th and $i+1$-th section and find the minimum. The program for $n=m=3$ ...
698 views

### Finding the midpoints of an ordered list of numbers

Suppose that I have an ordered list of numbers. The numbers in the list may be evenly spaced, but they may not be. Here are two examples, list1 and ...
215 views

### Getting a usable expression tree

I need to get the expression tree for some expression. expr //TreeForm The above grabs the expression tree but it isn't in some sort of usable format. Just an ...
121 views

### Style changes between controls and graphics

In the following Manipulate, the style (font?) of the a changes between when it is a control label and when it is a label in the graphics. Is there a way to make ...
332 views

### Manipulate Plot and control variables using multiple controls

Here's a simple Manipulate example: ...
270 views

### Getting vertical bar of equal length for | a || b | in a notebook

How can I make |a|*|b| show well in a notebook? I typed | from keyboard to denote absolute value. General cleanupIt will auto adjust by matching in my notebook so that sometimes it will not show as ...
497 views

### Why doesn't FindRoot work correctly?

I'm trying to find the roots of the following equation: I need to find λs for different values of ξ. I know that for all ...
523 views

### Removing not-a-number entries from an array of numbers

I have a list of {x, y, z} coordinates from a wavefront sensor I'm working with. However, not all of the imported points have actual values, but they still get ...
592 views

### RSolve Lotka-Volterra: A Closed Form Solution to this Difference Equation?

I would like to solve a difference equation, a Lotka-Volterra difference equation. I tried a model from http://www.stolaf.edu/people/mckelvey/envision.dir/nonDE.lotka-volt.html Using their ...
124 views

### Efficient Generation of Subgraphs (or, unfriend a friend a day)

NB: If you're not interested in the back-story, you could simply jump forward to the code which I'm seeking to optimize. Also, I believe this code would only work for MMA 8.0 and above. My friends ...
302 views

### ListDensityPlot performance when scaling axes

I need to visualize 3D data having 200*200 data points. ListDensityPlot is a good candidate, but it seems to have strange performance issues. I created a small ...
712 views

### Why isn't autosave enabled by default?

While I've come across several ways to implement/enable autosave (see: Is there a notebook autosave frequency configuration?, Saving my code before cell evaluations: Insurance against front end ...
182 views

### Character display color

I'm looking to cause the front end to display individual characters in a specific color, just in general, as a default sort of thing. For instance, the character "1" would always display as a red 1, ...
848 views

### Inverse of a polynomial in a polynomial ring

Let $N$ be a prime, and $q$ be a positive integer. Given a polynomial $f(x)$ in $R = \mathbb Z[x]/(x^N-1)$, I want to find another polynomial $f_q(x)$ in $R_q = \mathbb Z_q[x]/(x^N-1)$, such that ...
301 views

### Filling and Shading an Harmonic Curve

Suppose I have an equation plotted as shown: ...
145 views

### Why is this code in functional style is slower than procedural style?

I know that in Mathematica a functional programming style is often more efficient than procedural style programming using For loops. But the code shown below seems ...
388 views

### Create a table with inline conditions

I am trying to create a table with conditionals inline. For example, I'd like to create a 2 dimensional table like this: ...
162 views

### Minimize failing on a polynomial

Calling: Minimize[{-0.4877 - 0.1190 r^2 - 0.1885 r^4 + 2.9703 z - 0.5531 z^2, 0 <= z <= 3.5 ∧ 0 <= r <= 1.75}, {r, z}] returns ...
156 views

### Raster with ColorFunction is blank when Dynamic Updating is disabled

UPDATE Today I was having these WaveletScalogram problems again. I think this is ultimately some kind of interaction issue with Dynamic. I have narrowed it down to ...
458 views

### ComplexExpand absolute squared

ComplexExpand[Abs[a + b I]] Gives $\sqrt{a^2 + b^2 }$ ComplexExpand[Abs[a + b I]^2] On the other hand gives Abs[a ...
161 views

### Padding plot ticks with zeros on the right

I would like to know how can I make a real-valued plot tick pad with a zero to the right of the decimal point on integer values. This is what I have: ...
287 views

### Plot an undefined function

When I plotted an undefined function, Mathematica also spends considerable time to process it. It returns a blank figure necessarily. What confuses me is where the ...
240 views

### Convergence and value of a complex power series

I've done a little math and I got the following power series expansion of $\log z$ about $z_0=-2+i$. $$\log z=\log(-2+i)+\sum_{n=1}^{\infty}\frac{(-1)^{n+1}}{n(-2+i)^n}[z-(-2+i)]^n$$ I've shown that ...
146 views

### Unexpected side effect of removing the Orderless attribute from Times

First I make Times orderless: ClearAttributes[Times, Orderless]; Then I evaluate ...
397 views

### Preparing data for making an ErrorListPlot

I often have the following notebook in Mathematica, which I use to make a dataset and associated errors: ...
251 views

### Using the LQGRegulator to build a human operator model

I'm trying to build a human operator model using an optimal control model in Mathematica: The vehicle dynamics are given by ...
769 views

### Plotting a vector field

Can I somehow plot a vector field and the scattered data point associated with each and every vector? Also, is there any way to prevent Mathematica from interpolting the vector field? I am trying to ...
3k views

### Transform 3D data into 2D color map like Matlab's surf/imagesc

I have a bunch of 3D data (x, y coordinates and values) which is generated in Matlab and I need to render them in a 2D color map with certain axis ranges. Here are the Matlab code and the generated ...
274 views

### Remove the white margins of a Graphics3D figure

If the option Boxed is set to be False in Graphics3D, additional white margins may appear as ...
130 views

When considering this question about re-formatting Cell (also this one), I encountered an issue which confuses me. I'll let the code itself speak: Consider the ...
206 views

### Updating the format style of input cells from an older/'pre-styled' notebook

I have been given a large notebook that was created in mathematica 6. It contains a structure of sections and subsections and the input text is formatted in an unusual (possibly just old) style (see ...
269 views

### Partition a set into $k$ non-empty subsets

The Stirling number of the second kind is the number of ways to partition a set of $n$ objects into $k$ non-empty subsets. In Mathematica, this is implemented as ...
2k views

### How do I plot a solution of a differential equation?

I am having trouble generating a plot for a solution to my differential equations. I always end up with just blank axes. ...
193 views

### Why does Assuming for Integrate not work as expected?

I'm trying to perform the following integral with Mathematica 7: ...
3k views

### How can I solve this PDE with initial conditions?

I wish to solve the following second order partial differential equation $$u_{tt}=c^2 u_{xx}$$ with the initial conditions $$u(x,0)=e^x,\quad u_t(x,0)=\sin x$$ In Mathematica, I evaluated the ...
217 views

### Button doesn't evaluate variable containing Module

I have a huge set of code to accomplish a data transformation. I have saved this set of code as eg: ...
211 views

### How can I create a CDF application while using GUIKit?

I have created a notebook that uses GUIKit to create a user interface. The targeted user does not have Mathematica available so I thought about using the CDF player to convert the file if possible, ...
366 views

### What is the most efficient way to add zeros to end of a number?

Beside *10^n, is there a faster way to add thousands of zeros to end of a number? Updated Timings: ...
211 views

### How can I create a custom control which evaluates to a list of values or replacements?

I have a set of variables which are used in various places in my calculations (solving a system, initial conditions, etc.). In order to make this easier to deal with, I want to make a control-like ...