# All Questions

133 views

### What would be a pattern for a general row of an identity matrix?

I know this is a novice question but I would like a pattern for a list containing zero or more zeros followed by exactly one 1, followed by zero or more zeros. Something like: {0___,1,0___} But ...
436 views

### Problem when defining function through NIntegrate and NDSolve and Interpolation - Bug?

More than a single question, I have some doubts about the output of certain functions when defined through the result of other calculations. I am an active user of Mathematica, but maybe I haven't ...
70 views

### How to create a numerically “equal” function?

A simple example about what I need to do. For example, I have three functions: t1[x,t] t2[x,t] t3[x,t] and, ...
514 views

### Mismatch between numerical and analytic evaluation of an integral

I evaluated the following integral $$\int_0^1 \sqrt{r} \left | \cos \left(\left(k+\frac{1}{2}\right) \pi r\right)\right | dr$$ ...
535 views

### ContourPlot - unequal contour spacing

how can i specify the contour spacing or how the color range is distributed amongst the function values? Let's say i plot some function depending on x and y. Function values differ between [0, 1]. I ...
305 views

### unlisting a nested list

I have a list like this: list = {{a,{1,2,3}},{b,{1,2,4}},{c,{{1,4,5,5},{6,3,2,1}}}} This is a nested list which each element has a name. I want to export it to ...
132 views

### Is Mathematica 10 color managed?

With ColorProfileData[] Mathematica 10 can handle device-dependent color spaces. However, images with embedded color profiles, e.g. sRGB, are rendered and displayed ...
122 views

### Removing some data and replacing them with new ones

I have a data list where the elements have the form (time, velocity ). I need to remove some malformed elements in places where the data does not change smoothly and then replace those points by ...
112 views

### Strange behaviour of UpSet [duplicate]

Can anyone explain what is going on here? I want to modify TensorRank for IdentityMatrix, but it fails on its first attempt: ...
149 views

### Quartic equation [closed]

After using Solve I am choosing the physical root of my equation and dealing further with this root. However, when I am changing parameters using Manipulate, I clearly see not smooth behaviour. Is ...
124 views

### Dealing with square roots [duplicate]

Consider following expression: $$\sqrt{-\left(2 \sqrt{x^{-8/3}-x^{-4/3}+1}\, x^{4/3}+5\right) x^{4/3}+4 \sqrt{x^{-8/3}-x^{-4/3}+1}\, x^{4/3}+2 x^{8/3}+5}$$ In code: ...
326 views

### Plot “OilReserves” using CountryData from 1985 until 2014

I am newer using Mathematica to plot with the Function: CountryData, I am trying to plot "OilReserves" in "UnitedKingdom" from 1985 until 2014. I don't know how to do it, please help me!
191 views

### Replace a value in a nested array

When I run the following, ...
167 views

### Why is Mathematica 10 giving me the junk data from Instagram?

Instagram: instagram = ServiceConnect["Instagram"] ServiceExecute[conn,"request",params] sends a request to the connection identified by conn, in my example ...
141 views

### Finding the maximum order derivative of an expression

I have an expression that is the the sum and product of undefined derivatives and their derivatives. e.g. fg+ Dt[f,t]g +Dt[g,{t,2}]f+ What I would like to find ...
142 views

### Create composite key - operating across rows in a dataset

I would like to be able to create a new dataset by extracting 2 columns to make a composite key, and also extracting other columns. For example, suppose my dataset looked like: I would like to ...
90 views

### Take a list with the amounts of the random samples from another list while holding the index

I have a list called cant with some amounts of samples to take from the list community as follows: ...
236 views

### $SU(4)$ Structure constants in mathematica

How can I write a mathematica function which will output arbitrary structure constants of SU(4)?
1k views

### Join two datasets on keys

I want to be able to join two datasets by keys, pretty much like I'd do in SQL. I thought the JoinAcross function might do it, but it doesn't operate the way I thought. The example in the ...
234 views

### Plotting in projective space

I am having difficulty figuring out how to plot to projective space. Suppose I have a region which I have plotted such as: ...
104 views

### Running “Animate” Using a Button

I made the button below for launching an Animate, but it doesn't work at all! Why? ...
274 views

### Maximizing Large Multivariable Function over Region with Parameter Constraints

Brand new Mathematica user here. I have a complicated function to maximize, and thought I would try software like Mathematica instead of taking derivatives by hand. I found some Mathematica ...
574 views

### Solve ODE $d^2u/dx^2 + u/A = 0$

How can I solve following ODE with Mathematical: $$d^2u/dx^2 + u/A = 0 \quad (\text{or } \ C),$$ with the conditions: $$\left.\frac{d^2u}{dx^2}\right|_{x=0} = 0,$$ $$u(x=0) = B$$ and ...
233 views

### First pair out of order

I would like to know how to efficiently determine the first pair of elements in a list that are not in order according to some predicate p. That is, list[i] > list[j] according to p, and i is the ...
395 views

### Postfix with two arguments

This must be duplicate but can't find any related post. I'm want to pas it two argument in postfix like f[a_,b_]:=a+b; 1,2//f ...
185 views

### Copy As PDF in MMA 10

Wondering if this is a known issue.. I usually export graphics and Grids using the Copy As PDF menu item. The results looked quite good in MMA 9 on Yosemite. However in MMA 10 on Yosemite, the PDF ...
737 views

### Parsing a CSV file using Interpreter

The new Interpreter functionality in version 10 looks like it has the potential to make parsing custom data formats very easy. I'm trying to create a CSV parser. ...
167 views

### Matrix manipulation

Thank you for looking and answering this question. I am trying to create a new matrix from an old one. Meaning, I have a original matrix that's 20x20. I want to keep the first five lines of the ...
160 views

### Cross-validation of a FittedModel

Although I would know how to perform cross-validation tests after fitting a model using a function like NonLinearModelFit, I wonder if there is a way to do this providing the right parameters to the ...
110 views

### ClassifierInformation's “ClassPriors” misreporting?

To the TLDR people It seems to me that when you explicitly set ClassPriors when running Classify, it creates a ...
131 views

### How to define a variable updating function? [duplicate]

I tried to program a Sudoku solver when I suddenly ran into this problem: I need a function which effectivley does this: ...
198 views

Suppose a function such as: $\phi^{\alpha} (x,y) = \left\{ \begin{array}{l l} \alpha x & \quad \text{if$x < y$}\\ x & \quad \text{if$x = y$}\\ \alpha x + (1 -\alpha) & ... 8answers 492 views ### How to sort my list? For example I have two lists of such structure L1 = {{"Australia",a1}, {"USA",a2}, {"Norway",a3},...} L2 = {{"Russia",b1}, {"Norway",b2}, {"Japan",b3},...} I ... 1answer 191 views ### WhenEvent “StopIntegration” problem The first example on the WhenEvent help page is ... 7answers 213 views ### List creation/manipulation I'd like to a create a list from A = {{a}, {b}, {c}} by taking each elements n times in the following form: ... 2answers 600 views ### Positioning Vertices in a Graph I made a graph that has a given number at each vertex: I want to place vertex 1 above vertex 2 if value of vertex 1 is larger than of vertex 2. And also, vertices with same value should be located ... 2answers 170 views ### How to integrate a function which is only known at discrete points I have an integration to do. I want to integrate.$\int_0^\infty sin^2(2\pi t)f(t)dt$where$f(t)$takes values from an array in the form$\{t,f(t)\}$The time steps in the array is 1.1s. Can you ... 2answers 1k views ### PlotLegends -> “Expressions” not working when Plot given one function I don't get a legend when I use the option PlotLegends -> "Expressions" when the first argument to Plot is a single function. It works OK when I give ... 1answer 96 views ### How to provide data to users in a way similar to Mathematica's curated data How can one go about implementing a custom data backend usable by Mathematica? For example something like CountryData or ... 2answers 492 views ### What is a “Region” in Mathematica 10? "Region" seems to be a very important concept in Mathematica's latest version. Where can one find the more thorough introductory details about the concept of Region ... 1answer 158 views ### Fix the size of vertices and arrow in graphs I defined an option to draw nicely the graph. But I have a problem with the different size obtained. For example, the layout of the first graph is what I want to have for all other graphs I will ... 2answers 471 views ###$RecursionLimit::reclim: Recursion problem

Please, find bellow my original question. Here is all my code: ...
267 views

### Potential hill simulation

I attempted to simulate the motion of a particle approaching to a potential hill. The particle should experience a force of -1/r^2, if the equation for the ...
89 views

### Generating an Array of Vectors

I'm working a lot with nested lists of $(x,y)$ coordinates (of a FEM-like mesh, but that's not important), like so: ...
254 views

### How could I make an Excel-like table?

I am looking to build a simple Excel type of a table with four columns. I have spent some time researching Mathematica documentation, but haven't come across a way to implement that. Here is a ...
190 views

### Check if a scalar falls within the range given by sub-arrays of a matrix

I have a rank 3 matrix: r = {{{1, 10}, {19, 71}, {111, 159}}, {{1, 5}, {25, 63}, {118, 132}, {164, 185}}, {{1, 19}, {28, 49}, {157, 203}}}; and each of the ...
182 views

### NDSolve with Table and Boundary Conditions

I am trying to implement a 1D model of coupled field equations where I split up space into pieces to get a system of coupled ODEs which I call Eeqns and Ieqns. The problem I can't figure out is how to ...
359 views

### Importing Output from Linux mpstat to Calculate Aggregate and Per-CPU Averages, Creating Tables and Graphs

I'm a Mathematica noob, running a trial version for the moment, but have run into the wall trying to handle this in Excel and am looking for other options. While running a benchmark application I'm ...