# All Questions

265 views

### Can I generate a “piecewise” list from a list in a fast and elegant way?

Suppose we have a number list a: n = 1000000; a = RandomReal[{0, 1}, {n}]; We want to generate a list ...
153 views

### Defining and evaluating new continuous distributions based on Mathematica's distributions

A number of functions operate with Mathematica's set of distributions e.g. Through[{Mean, StandardDeviation, Variance}[UniformDistribution[{umin,umax}]]] which ...
407 views

### How to express an expression with only ArcTan and ArcTanh?

I have an expression which is simply (j/k) x^(j/k) LerchPhi[x,1,j/k)] where 0 < j < k. Manually I have been able ...
98 views

### Operations on expressions within Hold [duplicate]

I want to convert {Hold[1 + 2], Hold[3 + 4], Hold[5*6]} into Hold[{1 + 2, 3 + 4, 5*6}]. I have tried ...
104 views

191 views

### how to improve efficiency when I want to classify a list according to certain laws

I have a function that generates lists: f[n_] := Join @@ Permutations /@ PadLeft@IntegerPartitions[n]; For example f[3] ...
233 views

### Generation function of recurrence sequence

I'm trying to find generation function of recurrence sequence ...
138 views

### Evaluating Abs'[2 x] gives different results than evaluating D[Abs[2 x], x]

I noticed the following difference Assuming[x ∈ Reals, FullSimplify[D[Abs[2 x], x]]] (* 2 Sign[x] *) Assuming[x ∈ Reals, FullSimplify[Abs'[2 x]]] (* Sign[x] *) ...
253 views

### Grid ItemSize is smaller than expected

If I execute MatrixPlot@IdentityMatrix@100, the result is a good size. However, if I evaluate ...
119 views

### How do I assign specific data points in an array to a new array?

I am trying to learn how to script/program in mathematica and I am retyping some simple C and FORTRAN programs into Mathematica as a way to learn. I am writing a Monte Carlo code to calculate the ...
340 views

### My black text isn't black after exporting to PDF

Consider any standard plot, with true CMYK black text: ...
220 views

### Solving an exponential multivariate equation

I have the following equation: p = 1/(1 + E^(-51.179 + 0.849 x1 + 2.3649 x2 + 1.155 x3 + 1.46 x4 + 1.31 x5)) and I want to find the set of values for x1 to x5 ...
442 views

### plotting xy, yz, zx plane at

I have a data list in the following form, data = {x, y, z, f} I would like to present three kinds of subdata set as a density (or contour) plot on the ...
267 views

### finding anagrams

What I'm trying to find are the 4 letter words in the mathematica dictionary that have the most anagrams and the amount of anagrams these have each. But I can't seem to find all the 4 letter words in ...
44 views

### How to multy-Set a group of lists?

I have a group of lists, for example: lists = RandomInteger[10, {100, 2}] {{6, 7}, {7, 4}, {3, 3}, ....} Now, I want to ...
182 views

### How to return the rhs of a transformation rule from within Compile[]

I have defined the following function: ...
78 views

### map rational number [duplicate]

I am trying to map this function ((-1)^(1/Denominator[#]))^Numerator[#]==(-1)^#& to a fairly big list of random rational numbers I am trying to get this to ...
83 views

### Is it possible to merge cells excluding results with one click?

Now when I merge two cells with right-click "Merge Cells", they merge with the results included, while I only want the commands merged. Can I make it a one-click button? Now I have to delete the ...
89 views

### Plot producing many error messages when given complicated function

I'm new to Mathematica and am running in to all sorts of silly difficulties with coding in it. I'm trying to calculate a function f[x, k], normalise it with another ...
355 views

### Draw plot with locator & slider

I would like to create a plot whereby both the slider and the locator 'draw' the plot. In the following code, the locator & the slider act independently: ...
247 views

### Visualization of iteration procedure in NMinimize

I have this optimization code: ...
128 views

### Strange behaviour of Internal`InheritedBlock

I was going to post an answer for fast way to replace all zeros in the matrix. I was even quite happy because timings were the same order of magnitude as others. The idea was to overwrite ...
85 views

### What's wrong with my implementation on CountryData

I was wondering, *for which countries is the proportion of Phone line users to population greater than or equal to that of the United States?* This is what I inputted below, but the list of countries ...