10
votes
2answers
290 views

Conditional Gathering of lists

Just need a little help with the GatherBy / SplitBy function(s). I have a list of random numbers here: ...
10
votes
2answers
494 views

Creating randomly oriented planes

I would like to create randomly oriented planes. This is how I'm attempting to do that: I create a 2 random unit vectors, $\mathbf{v}_1$, and $\mathbf{v}_2$, in the $x$-$y$ plane I assume that if I ...
9
votes
1answer
191 views

How to define function that can change patterns

Given time series data as follows: data = {{{2011, 1, 13}, 10}, {{2011, 2, 14}, 17}, {{2011, 3, 15}, 20}, {{2012, 1, 16}, 30}, {{2012, 2, 17}, 40}}; ...
9
votes
5answers
449 views

How to choose three points on the circle so that the triangle is not a right triangle?

I want to choose three points $A$, $B$, $C$ has integer coordinates on the circle $$(x+2)^2 + (y+1)^2 = 25$$ so that the triangle is not a right triangle. But I can not. I tried ...
9
votes
6answers
390 views

Performing Computations on Sets

I would like to find a permutation of $\quad S=\{\frac{1}{10}, \frac{1}{2}, \frac{4}{7}, \frac{3}{5}, \frac{2}{3} \}\quad$ that maximizes the sum of theses elements raised to unique powers: ...
9
votes
0answers
133 views

Compile not correctly initializing a variable defined inside Module

In the following example, inside the minimumX's Module, x is initialized to 1, but the ...
9
votes
1answer
207 views

Why is ReplaceAll behaving like this?

I'm learning to use the ReplaceAll function and I found the behavior of which is quite confusing. For Sqrt[f[x, y]] /. f[___] -> u Mathematica returns ...
9
votes
1answer
577 views

Functional programming and Do loops

I'm writing a Monte Carlo simulation. I'm using a Do loop to create the different simulations, iterating over different ...
9
votes
1answer
267 views

Defining Tags in Reap

I am trying to use Sow/Reap to replace Append in my code. The problem is that I need to ...
9
votes
3answers
771 views

BarChart frame labels

This barchart was tricky to style, and I had to resort to the legacy BarCharts`package. Any ideas how to omit the labels from the bottom edge? Ideally I'd also like ...
9
votes
1answer
212 views

What default theoretical distribution does Mathematica use in PearsonChiSquareTest?

I used Mathematica's function PearsonChiSquareTest to test whether the data were drawn from a normal distribution. As in the reference, I expected Mathematica to compare the result to a normal ...
9
votes
5answers
231 views

Fill out blanks with a upcoming number in a list?

I have a bunch of arrays looking like this: {"", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", ...
9
votes
2answers
926 views

InterpolationOrder for ContourPlot

How do I acheive something like InterpolationOrder in ListContourPlot for ContourPlot? My ...
9
votes
4answers
1k views

How to sum up subelements of a list of unknown length

I'm simply looking for the {}+{} function for sublist elements of a list: (Parallel sums of elements) ...
9
votes
3answers
718 views

How do I change the Font in BarChart Legend?

Just wondering if anyone knows the proper Syntax to change the Text properties in the BarChart's ChartLegend. I cannot seem to figure out how to get Style[] to apply. Here is an example: ...
8
votes
2answers
239 views

Nest , Fold … is there an extension for more than 2 arguments?

Fold is an extension of Nest for 2 arguments. How does one extend this concept to multiple arguments. Here is a trivial example: ...
8
votes
2answers
301 views

How can I get $(r^{1/x})^x$ to simplify to $r$?

Simplify and FullSimplify do not simplify this kind of expression: $(r^\frac{1}{x})^x$. Consider ...
8
votes
10answers
332 views
8
votes
2answers
108 views

Alternative to NotebookLocate or NotebookFind

In Mathematica 8.0 and older, there are two ways to select cells based on cell tags. NotebookLocate["CellTag"]; NotebookGet[EvaluationNotebook[]] and ...
8
votes
1answer
339 views

How to align two overlayed plots, one being rotated?

I have two plots which I want to present on a single figure. The bottom left corner is a point of origin of the first plot. The top right corner is a point of origin of the second plot. Also, the ...
8
votes
1answer
117 views

Is it possible to use the global definition of a symbol as part of its new local definition set in a Block?

Consider the following expression: Block[{Print = CopyToClipboard}, doSomething[]] Now all calls to Print from ...
8
votes
5answers
249 views

Wrapping a function in count

I am working through the Programming Paradigms via Mathematica (A First Course) and am attempting to answer the following: Use recursion to count how many times the argument can have its square ...
8
votes
2answers
382 views

How do I create an ellipse bubble chart?

I have some data that I would like to plot as a bubble chart. The data is formatted as {{val1_mean,val1_sd,val2_mean,val2_sd},{val1_mean,......}}. What I would like to do is plot a bubble chart where ...
8
votes
1answer
202 views

How to automate x[i]→x_{i}?

I have several Mathematica expressions in which subscripts are expressed with square brackets. E.g. x[12] is meant to represent x12, etc. If I evaluate ...
8
votes
4answers
471 views

Efficient code for the Ten True Sentences puzzle

I am trying to solve Ten True Sentences Puzzle. Take a look at the following sentences: The number of times the digit 0 appears in this puzzle is _. The number of times the digit 1 ...
8
votes
3answers
356 views

Import values from tab separated file, change decimal point?

I have files that look like this: ...
8
votes
2answers
220 views

Change associativity of the @ operator

The @ operator in Mathematica is right-associative by default, i.e. f@g@h evaluates as f@(g@h) Is it possible to make the ...
8
votes
2answers
257 views

Differentiating an unknown solution to a PDE

Sorry if this question is too basic -- I'm not very familiar with Mathematica. I am interested in a way to systematically address the following sort of problem: Suppose that $u=u(x,y)$ is a function ...
8
votes
2answers
457 views

Expected Value: Strange/unexpected result

Assume $X$ is an exponential random variable with unit mean ($f_X(x)=e^{-x}$, $x>0$). I want to calculate the expected value of $\frac{1}{X}$. Since $X>0$, I am expecting that ...
8
votes
1answer
340 views

Efficiently Constructing Rank One Approximations for a Matrix using SVD

Suppose I have a $m\times n$ matrix $A$ (real for simplicity). Then SingularValueDecomposition[A] yields 3 matrices $U$, $\Sigma$ and $V$ such that $A = U\Sigma ...
8
votes
4answers
2k views

What is the cleanest way to prevent divide-by-zero warnings?

If I evaluate {1, 2, 3, 4}/{5, 6, 0, 8}, obviously I get one warning: ...
8
votes
1answer
361 views

Random variables with transformed discrete distributions cannot be applied to Probability[] function?

I have two discrete uniform distributions over same support: Dx = DiscreteUniformDistribution[{-8, 8}]; Dy = DiscreteUniformDistribution[{-8, 8}]; I use ...
8
votes
1answer
300 views

Why does Mathematica choose the second function definition?

While working on a solution to this question I've come across a case where I simply don't understand Mathematica's behaviour. I've got the following definitions: ...
8
votes
3answers
340 views

Can this code be written in a more functional style

Referencing this question, I wonder if the following code can be written more concisely using a functional style, i.e. without For loops or ...
8
votes
2answers
433 views

How to set row height in Grid?

I always thought that Grid (and the underlying GridBox) and the general handling of tabular objects is a bit weird in ...
8
votes
1answer
394 views

CDF and personalized style

I recently created a custom stylesheet. I then created a notebook with the new style, confirmed that the notebook had adopted the style, and then saved a copy in CDF. But when I opened the CDF in ...
8
votes
2answers
611 views

Mathematica rule substitution memory

First I present the specific programming question, and then I provide further background details. Given an expression in Mathematica, say f=3x+7y, there are two ...
8
votes
4answers
796 views

Automatically counting the number of lines of code in a set of notebooks

How can I automatically count the number of lines of code "Input" existing inside all the notebook files contained in a specified folder? I know there is the issue of considering or not the automatic ...
7
votes
2answers
219 views

Why do I get a different value when I change the order of integration?

I think the following two-dimensional integrals should be equal, since they both integrate the function over the half plane defined by $t>\tau$. $$\int_{-\infty}^\infty \mathrm{d}t ...
7
votes
1answer
200 views

How does LocationTest choose its “AutomaticTest”?

Is there a way of determining how LocationTest chooses its "AutomaticTest"? Sometimes it's clear from the ...
7
votes
2answers
163 views

How to un-eat memory?

Consider this code: ...
7
votes
4answers
246 views

How to make Mathematica simplify $\cos[(i + j + k)\pi]$ to $(-1)^{i+j+k}$?

We know that: $$ \cos\left[(i+j+k)\pi\right] = (-1)^{i+j+k} $$ for $i, j, k$ being positive integers. In Mathematica I've tried: ...
7
votes
3answers
296 views

How do I create a histogram with unequal bin widths?

I would like to create a histogram for human population by age, but the $2010$ census data I have available is for five uneven cohorts: ages $0$-$17$, $18$-$24$, $25$-$44$, $45$-$64$, and $65+$. My ...
7
votes
2answers
155 views

How do I define an argument pattern for a Head of NOT a given value?

I want to define a function f with an argument that matches only when an argument Head is NOT of a given value. I know I can define a pattern that matches the Head for an argument: ...
7
votes
2answers
1k views

Labeling points of intersection between plots

There are several answers where Mathematica used mesh points to show graphically where curve intersections exist. For example: Marking points of intersection between two curves or Is there a better ...
7
votes
2answers
135 views

How to ignore list elements when extracting with pattern matching

If I have a simple list, say {1, 2, 3}, and I want to extract a subset of the elements, what is the correct syntax? e.g. { i, _, j } = {1, 2, 3} I want i = 1 ...
7
votes
1answer
121 views

What should I call the messages that appear when the mouse moves over failed graphics output?

I attempted to evaluate the following Plot[x^2, {x, 1, 2}, PlotStyle -> {RGBColor[a]}] which, of course, failed. After the failure, putting my mouse over the ...
7
votes
1answer
136 views

Specifying optional arguments with variables

Perhaps this is poor programming on my part, but I would like to create a function that uses a variable as an optional parameter: var = 2; f[a_:var] := {a} The ...
7
votes
1answer
308 views

How to draw grid lines on top of a plot?

I want to use ArrayPlot instead of a DensityPlot because it seems to be faster (more here) I still want axes ticks to have real ...
7
votes
2answers
489 views

15 30 50 per page