# Tagged Questions

Questions about the use of built-in Mathematica functions, including pure functions.

47 views

### Computing an inexact derivative with some terms preserved in exact form

I am beginning to learn Mathematica and have the following question: How can I return a derivative with exact numbers instead of one involving numerical approximations? My original, single variable ...
664 views

### Create sine function with random increase in phase

I am trying to simulate a signal that randomly increases its phase, so far I have tried two thing but neither worked. I usually use matlab but I want to learn some Mathematica so I thought I would try ...
667 views

### Why does Hash return different values in Version 7?

This function does not work correctly for me. The generated Gravatars do not match the ones actually produced by using the corresponding address. The problem was traced to differing output from the <...
85 views

### understanding a mathematica equation

I have found the equation below written with Mathematica, I looked at the Mathematica online guide but it is still difficult to understand the equation. Can someone write this (or part of it) in ...
3k views

### Replacing functions

Given an expression expresion in terms of a function f and given another function g, how ...
169 views

### Expressions containing globally undefined symbols inside a function where they are defined

Consider the following code. f[a_,b_]:=x; Clear[a,b]; x=a+b; f[1,2] It returns a+b. However, from a certain viewpoint, one ...
122 views

### Missing zero in the CoefficientList

The following list has a length only 10 (not 11) CoefficientList[Series[ArcTan[x]/(1-x^2),{x,0,10}],x] {0, 1, 0, 2/3, 0, 13/15, 0, 76/105, 0, 263/315} It should ...
130 views

### Encapsulated plot function misbehaves

To insure a collection of plots has identical appearance, the plot command is encapsulated in a function. The results are undesirable. The fiducial plot is ...
568 views

### How is it possible to check if a function is even or odd?

I tried it like this: ...
196 views

### Converting multi variable expression into a function

So I have this rather complicated looking expression ...
152 views

### Defining Solutions to FindRoot a functions of parameters-Part II

Here's a similar question as the the preceding question with the same title, but this time with vectors, which I need to use. I followed the suggestion in the answer the the previous question, but it ...
5k views

### How to plot periodic function's graphic?

How to plot periodic function's graphic? For example, $f(t) = t$ when $-5<t<5$ and $f(t+10) = f(t)$. ...
214 views

### Major slowdown when using a ColorFunction with more than one named scheme

Problem remains in 10.1 Earlier Kuba noted a major slowdown with code Simon Woods posted. Here is a simplified example. First a color function using two different named gradient schemes: ...
484 views

### Using Functions as Arguments to Function

I am trying to make a function like Norm but defined like so: MyNorm[{x_,y_,z_}]=Sqrt[x^2+y^2+z^2]. Mathematica assumes that x, ...
69 views

### Which method to use for finding maximum without actually computing optimization function explicitly?

I am new to Mathematica and I am currently working on an optimization problem. The optimization function that I have easy to calculate for some assignment of variable but it is very difficult to ...
212 views

### I want to construct a function than the output is “Sequence”

For example if the input is x and x<10 the output is Sequence[x,0],if x>10 the output is Sequence[0,x] but obviously ...
505 views

### Using several anonymous functions mixed together

This works: list // BarChart[#[[2]], ChartLabels -> DateString @@@ #[[1]], ChartStyle -> "Pastel"] & This doesn't: ...
105 views

### How can I run a summation numerous times?

I have been working on code for finding the Allan plot of generated white noise, however, I cannot figure out a way to automate it for a different range of numbers. My code is as follows: ...
69 views

### Marginal distribution with weight

Given a multi-variate distribution $P(\mathbf{x},\mathbf{y})$, I would like to obtain the marginal distribution $$P_m(\mathbf{x})=\sum\int_{\mathbf{y}}P(\mathbf{x},\mathbf{y})W(\mathbf{y})$$ In my ...
644 views

### What are SparseArray Properties? How and when should they be used?

A strange undocumented form of SparseArray is increasingly used in answers on this site: ...
1k views

### Output of plots from within Do[ ] Command

I am wondering why the following does not plot the way it's written and exactly how does the Do[] function operate? I think I could be using it incorrectly. ...
121 views

### How to create fast functions based on units?

Using units is a good means for rapidly developing code, since it provides some error control. Hovewer, using Mathamatica functions containing units appears to be copmutationally inefficient. ...
399 views

### Prevent Export from overwriting files

Export["filepath1",Expression1] works for me, but if filepath1 already exists, it will be overwritten. I'd like ...
3k views

### Using a PatternTest versus a Condition for pattern matching

My last question to the site resulted in several answers that involve using pattern matching in Mathematica, a feature I wasn't very familiar with at the time. I am currently reading Mathematica ...
2k views

### What best practices or performance considerations are there for choosing between Cases, Position, Pick and Select?

Cases, Select,Pick and Position each have different ...
266 views

Observe: ...
199 views

### truncated square wave input

I'm investigating the response of some dynamic system on Mathematica and I want to generate a tailored square input like the one in the following picture: Does anyone know how to generate such input ...
75 views

### Computing large nested values

Is it possible to compute a value for n=10^9; Nest[# + Log[#] &, 2., n] for large n? $10^9$ seems to be the max for me - ...
130 views

### Continuity of function-example

I'd like to examine the continuity of the following function: f[x_] := Limit[(n^x - n^(-x) ) / (n^x + n^(-x) ), n -> Infinity] I know that this function isn't ...
129 views

### beginner's question: change a parameter while get variable answers [duplicate]

I'm new to Mathematica from R, since R is not quite good at dealing with the following problem. Say, i want to solve the function a x - 10 = 0. Each time I change the value of a, say, from 1 to 10 by ...
580 views

### Performance problems in new Sequence functions

The new-in-10.1 Sequence* family of functions should provide newly optimized methods for handling sequence problems. Happily in some cases they do! For example ...
108 views

### Get the sum with cases

I have the following list: list = {{1, 2}, {2}, {3, 4, 1}, {5, 4}, {3, 3}, {a, b, c}, {e, f}, {g}, {}, {Sin[a], Cos[b]}}; I should use ...
117 views

### Handy dates conversion

I feel like something very basic is missing me, $dateformat = {"Year", "Month", "Day", "Hour"}; date = DateString[$dateformat] DateString["Date"] ...
319 views

### What does IndexBy do and how exactly does it work?

I just saw the function IndexBy in the autocomplete suggestions and I was curious to know exactly how it works. Unfortunately, there's no trace of it in the ...
142 views

### How to construct a kernel from a function?

I would like to convolve an image with a mathematical function. I understand that I need to have the mathematical function in a matrix form. How can I build it? Thanks
236 views

### Creating a Cayley's table of square

I'm interested in creating a Cayley's table of square using Mathematica. I'm not a programmer but occasionally resort to using Mathematica to simplify my work insofar as the programming doesn't take ...
113 views

### Understanding FixedPoint

I understand that FixedPoint[(# + 2/# )/2 &, 1.] can be written ...
35 views

### Fibonacci series up to 300 terms [duplicate]

I tried to generate a list of Fibonacci numbers up to 300 terms and gets a runtime error. f[0]=0; f[1]=1; f[x_]:=f[x-1]+f[x-2]; Table[f[x],{x,1,300}] Is there ...
54 views

### Question about a catalytic equality?

I have a question on math.SE that explains how I came up with these equations. ...
71 views

### Two unrelated questions: 1. Output of Series[] for function, 2. Output conditional answers as if not conditional [closed]

As mentioned in the title, I have two questions. 1. I have code that looks similar to: ...
88 views

### Why minimization does not work with symbolic array as arguments

If I try to minimize with constraints a function of several variables, with Gamma regularized function involved in the constraints it seems to works, as shown below (this is just a dummy example ...
114 views

### Random Polynom Plot [closed]

I should write a module "RandomPolyPlot[n, amin, amax]" which calculates all roots (nulls) of a n-th degree polynomial function. Then I should illustrate it on the complex plane. I also should ...
101 views

### How to stop FullSimplify from returning Root objects

I have several expressions in a series, such as 1/4 (-(1/4) + Sqrt[5]/4 + I Sqrt[5/8 + Sqrt[5]/8]) (-1 - Sqrt[5] + 2 Sqrt[7/2 + (5 Sqrt[5])/2]) If I run ...
109 views

### Write a function, write a pattern [closed]

I have the following list: list = {{1, 2, 4}, 6, 7, 8, {8, 2}, {3, 4}, {4, 5}, {1, 2, 3, 1}}; (a) I should write a predicate-function in combination with an ...
40 views

### How can I put the results of TrigReduce function into a more convenient form? [duplicate]

a1 D11 Cos[n x] + a0 a1 D11 Cos[n x] + 1/2 a1 a3 D11 Cos[n x] + 1/2 a2 a4 D11 Cos[n x] .......for example this expression can be written like ('expression') * ...
154 views

### Optional arguments with lists as function parameter

I'm developing a function f which should support optional arguments {x_, y_} in list form. A simple example looks like this: <...
163 views

### How to run code in a saved file when it is opened

I have a Mathematica file that I saved. In it, I have multiple functions that I've defined and have evaluated a number of the functions with different arguments. I would like to be able to open the ...
290 views

### Create a function with Dt[x] as a variable

I have a function (for example F[x_]:=Cos[x]). I want to define a function like Fdot[x_,xdot_]:=Dt[F[x]] where xdot represents Dt[x]. For example, to define Fdot one might naivley try Fdot[x_,Dt[...