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

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0
votes
1answer
95 views

Help with functions in Mathematica

Still learning how to do things in Mathematica. I want to make a function that has many parts. Doing this in something such as Java, which I am familiar with, would be simple. In Mathematica I have ...
6
votes
1answer
265 views

How trustworthy is NMaximize?

Suppose I solve a constrained optimisation problem using NMaximize. How confident can I be of the accuracy of the result? For concreteness, suppose that F,G are ...
0
votes
2answers
61 views

Fitting data in form $f = f_0 + c A^x$

The Fit[] function in Mathematica can fit data in form of $f = f_0+c_1x+c_2x^2+...$ ($f_0$ and $c_i$ are unknown constants), is there a function can fit date in ...
8
votes
2answers
264 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 ...
0
votes
2answers
98 views

Is there a function that filter positive values x = f(x), and return zero for all negative values? [closed]

I'm searching for f that will comply this definition : x = f(x) where x is natural >= 0 0 = f(x) where x is natural < 0
0
votes
1answer
80 views

How to create a line due to requiriements?

Considering we have three lines, and know the intersection points (How to find intersection points of lines?) How can I draw a line that will cross the intersection point of the two lines and will be ...
1
vote
3answers
449 views

How to find intersection points of lines?

Considering I have three functions f1 = -x + 1; f2 = x - 1; f3 = x + 3; How can I find the intersection points of this functions? Thanks. This didn't work ...
0
votes
0answers
65 views

What is the product of 1+1/p^2 over all primes p? [duplicate]

Can Mathematica Sum or Multiply over the set of all primes? I can get an estimate of my question in the title with: ...
4
votes
3answers
249 views

Problem about an ant walking up a hill

An ant is walking up a hill given by $f(x)$. At what point can it see a blade of grass. I've been working on this problem with Mathematica and by hand. Help with either would be fantastic. The ...
1
vote
1answer
57 views

Using Inner to calculate a log likelihood

I am trying to use the function Inner to calculate the sum of log likelihoods of a custom probability distribution 'custom' applied to a vector of data 'vData'. The custom distribution changes ...
-2
votes
2answers
101 views

Plotting self-made functions [closed]

EDITED AS SUGGESTED I have defined a function, which takes two values and returns a function n(x), like so ...
0
votes
1answer
41 views

Summation of functions

I want to define a function that is a sum of other functions. For this, I define functions of the form ...
6
votes
2answers
145 views

Using MovingMap to calculate percentage changes

MovingMap (new in version 10) applies a function to discrete data over a moving window. This is very convenient for calculating the percentage change of a series. ...
2
votes
1answer
106 views

Dirichlet convolution of two lists [closed]

The Dirichlet convolution of two arithmetic functions f,g is defined by $f\ast g(n) = \sum\limits_{d|n} f(d)\ast g(n/d)$ How can I get the Dirichlet convolution of two lists? For example: Input: ...
0
votes
1answer
43 views

How to set a shared variable Power (a modified one)?

Unprotect[Power]; Power[0|0., 0|0.] = 1 ; Protect[Power]; Table[0^0, {i, 5}] No problem at all. ParallelTable[0^0, {i, 5}] ...
0
votes
1answer
72 views

Mathematica function to generate a different 4 digit number [closed]

I m looking for a function that permit me to generate a different 4 digit number (>0) each time (to 4^10 possibilities) corresponding to a parameter that will never be the same (like current ...
0
votes
0answers
63 views

subtlety of self-defined function and its evaluation [duplicate]

I wrote a simple code as follows f[x_,y_]:=NIntegrate[x+z,{z,0,1}]; g[x_,y_]:=NIntegrate[y+z,{z,0,1}]; VectorPlot[{f[x,y],g[x,y]},{x,0,1},{y,0,1}] then ...
3
votes
2answers
115 views

How to define a list of symbols as a list of functions?

I have a list in Mathematica for example P={1+t,1+t+t^2,1+t+t^3}; My question is, how I can define each element of this list be a function of ...
1
vote
1answer
61 views

Cannot use Part in Pure Function [duplicate]

I need to select some lists in the nested list of form of {{1,2,3},{2,3,4}}. I have used Select to complete my work. But when I tried Position, it doesn't work. For example, ...
1
vote
1answer
49 views

Mathematica defines a function as list

This might be a very silly question but i'm defining a function as: \[Chi][AR_] := ((AR^(2) - 1)/(AR^(2) + 1)); which is clearly a scalar function of AR; however ...
3
votes
1answer
101 views

Creating an autokey cipher function

Can someone help me with putting what I can say in words into code. I want to create autokey encrypt and decrypt functions (just wanting help encrypting and then can figure out decrypting). Everything ...
2
votes
0answers
76 views

Is there a documentation generator for Mathematica?

I'm looking for a way to document the functions of my packages inline, preferably inside comments. There should be a Doxygen type tool for this that takes comments and that generates html from markup ...
3
votes
1answer
213 views

Creating the Nabla operator as a operator

How can I define the nabla-operator as a an operator, acting on everything to the right of the operator! Also taking \[Del]^2 would give the second derivivates. I wish to be able to write ...
5
votes
4answers
202 views

Sort two lists at the same time, based on another

I am new to using Mathematica and I can not find a solution to what I am wanting to do. I want to take a list such as: x = {1,2,3,4,5,6,7,8} and a second list ...
1
vote
1answer
195 views

Shorthand for operations?

Mathematica has a large number of built-in symbols, and I am unsure when there is a shorthand for the operation I am trying to perform. Question 1: Is there a shorthand for the function ...
1
vote
0answers
59 views

Can Mathematica return the first few terms of a sequence given the first few terms of a Dirichlet Generating Function?

For example: a=Sum[1/n^s,{n,1,6}]; Expand[a^2] returns a big mess. I want to see something like: 1/1^s + 2/2^s + 2/3^s + 3/4^s + 2/5^s + 4/6^s + ... + 1/36^s.
2
votes
0answers
22 views

Determining default value from previous arguments [duplicate]

How does one specify a default value for an argument which is dependent on the previous arguments of a function? For instance, consider the function ...
1
vote
1answer
50 views

Function does not initialise variable as changes are made in the manipulate function

My function "DefineRss[]" takes in three arguments and outputs a plane value. It sits in the first argument of the function plot3D and that in turn sits in the manipulate function The function also ...
1
vote
1answer
76 views

Minimize under constraint on an interval

I want find the minima of a (multivariable) function under a constraint which has to be fulfilled on a whole interval, let's say $$ \nabla f (\underline x) = 0 \ \\ \ c(\underline x,s)\geq0\ \forall ...
1
vote
2answers
72 views

Evaluate list of functions at a certain point

I have a list of functions (actually they are derivatives) of the type: {D[g[x,y],x],D[g[x,y],y]} I would like to evaluate all of these functions at a point, ...
4
votes
2answers
109 views

DeleteMissing issues [duplicate]

Has anyone had problems with the DeleteMissing function in Mathematica 10.0.2? I find that it rarely works. Most of the time it returns a list which still contains ...
-1
votes
1answer
74 views

My code of plotting a two-variable function is too slow [closed]

I have a code in which my complicated function to be plotted is F(x,p). I would like to graph it for 5 values of p equal to 10^7, 10^8, 10^9, 10^10 and 10^11 for x values between 0.01 and 0.99. All ...
5
votes
5answers
260 views

What is primary, function computation or function application?

What is the order of computations here? g[x_]:=x^2; f[x_]:=Sqrt[g[x]]; Map[f, Range[100]] Does this code first get $f(x)=x$ and then gives its values or for ...
0
votes
0answers
142 views

Problem with FindRoot applied to functions

I am having difficulty with the error "is not a list of numbers with dimensions..." when using FindRoot (and other numerical routines in Mathematica) to solve equations numerically when the argument ...
0
votes
1answer
56 views

How can I change variable passed to a function? [duplicate]

Sometimes I'd like to make a function, which would take an argument "by reference" instead of usual "by value". This is semantically similar to what e.g. AppendTo ...
0
votes
1answer
91 views

Finding x when sin(x) = -.758 [closed]

I'm not understanding how to find all the angles for when sin(x) is equated to a negative decimal can someone explain to me how to find it..? So far I came up with 49.288 degrees, and 229.288 degree. ...
0
votes
0answers
68 views

Applying the square root of operator on polynomial functions

I am trying to apply an "operation" on polynomial functions: apply the operator $(\frac{\partial f}{\partial x}-y\frac{\partial f}{\partial z})^2+(\frac{\partial f}{\partial y}+x\frac{\partial ...
3
votes
2answers
131 views

What's real analogue for FromDigits?

FromDigits only works for integer strings. What's its real-number analogue?
14
votes
1answer
221 views

Compability between Graphics coordinates and shifted projections in GeoGraphics

Bug status V. 10.0.0 - V. 10.2 I'd expect GeoGraphics to handle positions of points since they are provided with ...
2
votes
2answers
191 views

Permanently rounding numbers/values to a given number of significant figures

I am searching for a simple way of rounding and setting an input to a desired number of significant figures. There are a vast number of posts that discuss similar problems, but none address this ...
2
votes
2answers
181 views

Polynomial expansion of operator

I am new to Mathematica, I am trying to generate the polynomial function of a operator. So for example, the operator $L $ is $\frac{\partial f}{\partial x}+\frac{\partial f}{\partial y} $, and I want ...
3
votes
1answer
57 views

LineScaledCoordinate problem for exact coordinates

Edit: Confirmed bug. CASE:2326540. Still the case in V 10.1. Solution: Wait and use N meanwhile. I've faced this problem ...
2
votes
1answer
84 views

How-to convert real number into List of its digits?

How could I convert a real number into a List of its digits in Mathematica? Example: 8.168643234 Desired output: {8,1,6,8,6,4,3,2,3,4} Many thanks in ...
0
votes
0answers
84 views

Numerical Integration/Function

I have a problem with a function defined numerically through an integral of the form: ...
1
vote
1answer
99 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 ...
0
votes
1answer
94 views

Recursive definition of nested sums

I have a set of functions which take lists as arguments. They recursively nest sums, and I have defined them as follows ...
4
votes
0answers
86 views

Using an external Pattern breaks Format

I noted while writing this answer that using an external Pattern on Format doesn't work: ...
5
votes
1answer
158 views

Is there a built-in function to do binary search?

Is there a built-in function to do binary search? Say, given a list (sorted) and a number, find the position which keeps the listed sorted when the number is inserted. I know that ...
4
votes
1answer
118 views

Display level of recursion of a recursive function during execution

Given a recursive function, is there some simple way to display or store the value of recursion or "how many levels deep" the function is at a given time? For instance, if we wrote the recursive ...