2
votes
1answer
254 views

Area between Contours in ContourPlot

I feel slightly foolish for asking this because I am so close, but I'm having trouble, so I will anyway. I asked this question two days ago regarding finding the lengths of contours. Now, I'd like to ...
2
votes
1answer
243 views

DynamicModule with Plots and EventHandler

I am making a little animation in Mathematica, along the lines of some of the Wolfram demo projects. I'd like to animate a simulated trajectory of a random process (say a Poisson process), and while ...
4
votes
1answer
210 views

Find lengths of contours in a ContourPlot

I am trying to find the lengths of different contours in the following plot: It is a complicated piecewise function evaluated on the unit disk. I am hoping there is an easy, generalized way to ...
11
votes
2answers
295 views

Rotational Averaging of Image Periodograms (FFTS)

I'm writing a code to do rotational averages of image FFT's. I have a working version but it is pretty slow. Wondering if anyone has any thoughts on a way to do this more efficiently. Data looks ...
0
votes
1answer
236 views

Infinite expression 1/0.^(1/4) encountered in NDSolve

I am trying to solve very simple system of coupled differential equations using the NDSolve function, but I am getting ...
-1
votes
0answers
60 views

Numeric function not fully evaluating

I'm running into an issue where it seems Mathematica is not fully evaluating the output of my function h[t_]. I included the definition of phi[t_] just to demonstrate that it is a numerically defined ...
26
votes
3answers
5k views

Can Mathematica do symbolic linear algebra?

For instance, is there some way I can say "let A and B be arbitrary real $m\times n$ and $k\times m$ matrices, Simplify[Transpose[Transpose[A].Transpose[B]]]" and ...
1
vote
0answers
48 views

How to determine three last bindings made to a variable when evaluating an expression?

How can I create a list of bindings made to a certain variable when evaluating an expression? I want to determine three bindings made.
1
vote
2answers
80 views

How to plot the product of the NDSolve result and any known function

How can I plot the product of the NDSolve result, e.g. x[t]/.solution and any known function, for instance, ...
2
votes
0answers
77 views

Does the VerticalCallout algorithm in PieChart work correctly?

This manufactured example is typical of many real world cases where we have thin slices of the pie: ...
0
votes
1answer
81 views
1
vote
1answer
112 views
1
vote
0answers
115 views

How to work with large numbers

How do I browse very large numbers in mathematica, say $10^{{10}^{{10}^{1.414\ldots}}}$? By browse I mean finding the $k$th decimal place before or after the decimal point. Everything I have tried ...
3
votes
1answer
59 views
5
votes
1answer
264 views

Variable number of nested variable-range sums

I would like to express the following nested sum in Mathematica: $$ S(m,j,N) = \sum_{k_1=m+j-1}^{N-1} f(N,k_1) \sum_{k_2=m+j-2}^{k_1-1} f(k_1,k_2) \cdots \sum_{k_m=j}^{k_{m-1}-1} f(k_{m-1},k_m) $$ ...
6
votes
1answer
420 views

Efficient JSON parser for Mathematica

Im looking for a efficient way of parsing JSON data in Mathematica. I am having a lot of problems with ImportString because it uses Java, is too slow, and uses too ...
0
votes
1answer
96 views

looping in mathematica for using the current value as initial state of next value [closed]

i have some initial state $psi[x,t]$. I perform some operation on it and store the value in another state $pi1[x,t]$. Now on the next step i have to use $psi1[x,t]$ as initial state and perform the ...
10
votes
3answers
679 views

Finding “Maxima” and “Minima” on a B-Spline

I need to find the "Maxima" and "Minima" on a B-Spline or more correct the points where the 2nd components of the derivate equal zero. For example: ...
1
vote
1answer
241 views

Plot of a periodic triangular wave

I'm trying to graph the zig-zag function at the top of this page: http://www.math.ubc.ca/~feldman/m321/nondiffble.pdf I have a little bit of experience with Mathematica but not a ton. Any ...
3
votes
1answer
186 views

Little triangles appearing in a Mathematica region plot with “opacity” saved in a PDF file [duplicate]

I am trying to produce a region plot of many functions, but Mathematica keeps showing me the little triangles when I save it as pdf. I have seen other solutions which fix the problem with PlotStyle-> ...
8
votes
2answers
672 views

How can I get Mathematica to simplify $\Vert\{1,\sin(t),\cos(t)\}\Vert_2$ to $\sqrt{2}$?

Context Norm[{1, Sin[t], Cos[t]}] Norm[{1, Sin[t], Cos[t]}] // Simplify (* Sqrt[1 + Abs[Cos[t]]^2 + Abs[Sin[t]]^2] Sqrt[1 + Abs[Cos[t]]^2 + Abs[Sin[t]]^2] *) ...
3
votes
5answers
391 views

Randomly selecting and reinserting a subset of elements in a list

This question is similar to my other question: How do I randomly select 'k' positions in a list and shuffle their respective elements without effecting the other elements? Imagine first a ...
0
votes
2answers
95 views

How to generate a list with a loop, and put it into a variable?

I am pretty new to Mathematica and to coding in general. I want to do a very specific thing, but I unable to do it. Please explain in detail how I can make this work. Here's the details on what I am ...
0
votes
2answers
227 views

How can I get a PieChart to be colored as I wish?

How to use the value of a funtion[label] to assign color to a piece of the pie? (edited after answer of kguler ) My dude is how to control the colors in ranges of a function of [labels] In this way ...
1
vote
0answers
43 views

How can I use the Rules returned by FindFit? [closed]

When I evlauate data = RandomReal[10, {5, 10, 2}]; fit[i_] := FindFit[data[[i]], a Sin[x] + b, {a, b}, x] fit[1] I get something like: ...
11
votes
4answers
305 views

Replacing parts of a held expression with held parts of another expression

I'm applying the Trott-Strzebonski technique in order to replace inside a held expression. ...
2
votes
1answer
353 views

Different Poincaré maps for same Equation

I've seen the Wolfram Poincaré example. I'd like to modify this sample in order to have a list of Poincaré maps. In the example the event is captured only when ...
-1
votes
1answer
68 views

How to loop in reverse order?(e.g. for i from 10 to 1) [closed]

I have a list F = {382.856, 638.53, 915.482, 1192.44, 1469.39, 1746.34, 2023.29, 2181.91} And I want to use it to calculate V: I think it should be something ...
4
votes
1answer
233 views

Butterworthfilter data filter

I am currently doing a signal analysis and filtering using Matlab. The filter I am using is Butterworthfilter model to filter scattered data (vector data). I am using Matlab as follows: ...
5
votes
1answer
253 views

Structure of curated data?

Is there a way to programmatically access the structure of curated data present in Mathematica (for each type of information, for example for CountryData or ChemicalData) that would allow access to ...
3
votes
2answers
178 views

Controlling spacing of histograms in Histogram3D

I have five histograms, hist1 = Histogram[data1, 20], to which I append {1, 2, 3, 4, 5} via ...
0
votes
0answers
81 views

About how Mathematica understands the branchcuts of the complex logarithm [Part 3]

One understands that for the function $\log(z^2+a^2)$ Mathematica implicitly puts the branch cuts to be starting at $\pm ia$ and going up/down respectively on the imaginary axis. The phase of this ...
10
votes
2answers
378 views

Select cases from a list

I have a list in the form : {1,1,1,0,-1,-1,1,1,1,0,0,0,0,-1,-1} No I'm trying to select only those sequences which start with 1 have a zero (or many zeros) ...
1
vote
0answers
33 views

Correct use of Mathlink's MLGetRealList

I am attempting to use Mathlink from C. I have managed to return single values from mathlink to my c program, but I am having trouble with lists. Consider the Mathematica operation: ...
2
votes
0answers
467 views

FindRoot in range

I am trying to find all roots in a range, using y /. FindRoot[Sin[y] == 0, {y, #}] & /@ Range[7] which gives ...
0
votes
1answer
151 views
0
votes
0answers
56 views

TableDirection in TableForm

I got confused about what does "the outermost dimension" and "the first dimension" mean in the document I snipped. Does it mean row or column?
0
votes
2answers
93 views
0
votes
0answers
100 views

Manipulate for Electric Field

I'm kind of new to Mathematica but I'm getting the hang of it slowly. Anyways, I'm trying to do a project on the electric field of two particles so my professor helped me with this code (sorry in ...
2
votes
1answer
62 views

How to distribute PermutationProduct over the sum

Assuming I have two elements of the permutation group algebra $a_1$, $a_2$ such that $a_i=\sum_{p\in S_n}\alpha_pp$, I want to define a linear product $\odot$ that distributes over the sum and pulls ...
0
votes
0answers
105 views

an NIntegrate inside a manipulate in mathematica was working and suddenly won't work now. it says indeterminent and it doesn't make any sense why

my title says pretty much everything heres what I'm entering. NumericQ returns a false value but it was true before. Im loosing my patience because this is so ...
2
votes
2answers
205 views

How to select the first “lowest” (first valley) number in a list?

I would to select the first valley of the list of coordinates below. It should be {3, 1}. ...
2
votes
1answer
174 views

Generating the set of all strings within a fixed edit distance of a initial string?

Provided a starting string initialString, and a particular alphabet of allowed characters {"A","B","C","D","E",...}, how can I ...
3
votes
2answers
117 views

How do we make a negative integer out of a string of a negative number and vice-versa?

Negative numbers are not taken into consideration by mathematica's built-in functions. FromDigits["-2"] Gives me this message: ...
1
vote
2answers
155 views

X-Y scatterplot

Hi I have a simple question. How do I plot the following with Day 1 as my X axis and Day 2 as my Y axis? I need the 22 variances plotted according to the Day they were taken from (these were ...
7
votes
1answer
144 views

Explain the difference between ViewPoint and ViewVector?

I've read the documentation, but am still very unclear as to what the difference is between ViewVector and ViewPoint for ...
1
vote
0answers
53 views

Conjugate of InterpolatingFunction?

From NDSolve, I got this: {{a1 -> InterpolatingFunction[{{0., 40.}}, "<>"]}} What would be a sensible approach to ...
3
votes
2answers
97 views

Finding all instances of length $N$ common subwords in two strings

Given a pair of strings, I'd like to return a list of all common subwords of a fixed length of "n" characters (i.e. contiguous subwords of length "n" that occur in both strings), allowing for ...
10
votes
4answers
299 views

Efficient way of identifying the indices of first occurrences

It seems to me like identifying the first occurrence of unique elements should take about the same amount of time as it takes to delete duplicates. My data sets are much larger than this (...

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