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

learn more… | top users | synonyms

1
vote
1answer
225 views

function returning 0

Why is my function returning 0? ...
1
vote
1answer
90 views

Issues with creating functions [duplicate]

Sometimes when I try to create a function inside a function, Mathematica gives me a hard time. I usually just have to play around with the syntax until it gets something it "likes" but I really have ...
3
votes
1answer
84 views

What is the syntax to combine conditions and options? [duplicate]

How can a condition and an option be written on the RHS of a function? I.e. ...
7
votes
0answers
163 views

Finding hidden treasure (aka finding undocumented functions) [duplicate]

I was searching for a way to determine if a point is within a polygon and stumbled upon rm -rf's answer. (actually, I really wanted to find a point within a ...
5
votes
2answers
1k views

How to find the non-differentiable point(s) of a given continuous function?

For example, the non-differentiable point of the function $f(x)=|x|$ is at $x=0$. How to find the non-differentiable points of a continuous function that is defined numerically?
8
votes
3answers
532 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 ...
1
vote
2answers
223 views

How to apply function f for each time value t, to each pixel from image, resulting in t images

I have a 2D array of complex values and I want to apply a function to every entry of the array, for every timepoint t in a list. I know how to apply my function to one entry for every time t in a ...
4
votes
1answer
269 views

Creating a function to simplify WolframAlpha query

When I can't remember an integral I usually just query wolfram and have it show steps. This was my naive attempt at trying to make a simpler function. ...
4
votes
0answers
104 views

Gather dependency on list order?

I get intrigued about Gather behavior on this post. I thought that Gather was invariant under list order? Here is the result I ...
10
votes
5answers
3k 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 $f(t+10) = f(t)$. ...
2
votes
1answer
129 views

How to define a function of z[bar], etc

Using Displaying index as subscript on output: e.g. C[i] -> C_i with Notation[...] or Interpretation[..]? I have often ended up wanting to define functions of annotated variables to better match my ...
1
vote
2answers
833 views
5
votes
1answer
193 views

Why does MapIndexed return the index in a list?

MapIndex returns the index in a list instead of as shown in my revised example. I can work with it (or work around it), but what's the design concept? It seems ...
4
votes
1answer
155 views

How hide symbolic definition of a function?

How can the actual definition of a function be hidden from a user? I want the user of a notebook to be able to evaluate a real-valued function f of a real variable at any particular numeric input yet ...
4
votes
4answers
423 views

How to find the maximum of a function on a set of discrete points?

How to find the maximum of a function on a set of discrete points? For example, what is the best way to find the maximum of ...
4
votes
1answer
354 views

Simplifying polynomials in non-commutative variables

I would like to be able to simplify a polynomial in two non commuting variables, the desired result being that in every term one variable occurs to the left of the other variable. An example would be ...
8
votes
2answers
782 views

Obtaining the name of a variable as a string [duplicate]

Suppose that I have an arbitrary variable myVariable. Is there some function fun -- either built-in or one that I can define -- ...
15
votes
8answers
412 views

Is it possible to use RandomChoice to choose without other choices being evaluated?

I'm trying to do this: i1 = 1; i2 = 1; RandomChoice[{ (i1 = i1 + 1), (i1 = i1 - 1), (i2 = i1 + 1), (i2 = i2 - 1)}] In order to chose randomly which ...
3
votes
2answers
1k views

How to enter an equation into FindFit?

I have the equation ...
1
vote
1answer
209 views

Using NMinimize Properly

I'd like to find the point on a Bezier curve that's closest to some other point. The tricky thing is that because Bezier curves can loop around, the distance function can have multiple local minima ...
2
votes
1answer
129 views

Why the EuclideanDistance of these 2 exact points generates the warning N::meprec?

The two points are: pts = {{1/4 (-1 - Sqrt[5]), Sqrt[5/8 - Sqrt[5]/8]}, {1/4 (-1 - Sqrt[5]), -Sqrt[5/8 - Sqrt[5]/8]}}; EuclideanDistance @@ pts ...
2
votes
2answers
95 views

How to make a function work on symbols in a specific context

Let us say we have two sets of symbols $(x, y, z)$ with the same names that live in two different contexts: ...
3
votes
3answers
255 views

How to find the numbers $a$, $b$, $c$, $d$ of the function?

I want to find four numbers $a$, $b$, $c$, $d$ of the function $f(x)= \dfrac{a x + b}{c x + d}$ satisfying the conditions $f(-6)=4$, $f(-5)=5$, $f(1)=3$ and $f(2)=2$. I tried ...
19
votes
1answer
216 views

How to get Cases to wrap results in an arbitrary head?

A number of functions provide for results to be wrapped in an arbitrary head. This is very important in cases where the results should not be evaluated. Take ...
0
votes
0answers
50 views

Phase Unwrap List Of Points: Implementing continuous phase/Arg function for List of Points [duplicate]

I am looking for a function to unwrap phase of a list of points as done here for the continuous case. I have the Re/Im data as my input and would like the unwrapped phase as the output. Does anyone ...
10
votes
5answers
534 views

How to find first list element that differs from average of N previous elements by more than a given amount?

Given a list of real numbers, I need to write a function that returns the value of the first element in the list that differs from the mean of the previous $N$ elements by greater than $P$ standard ...
10
votes
4answers
1k views

How to find the domain and range of an implicit function?

For example, we have this curve: $$ x^2 + y^2 = 1 $$ Is there a function in Mathematica for finding out that the ranges for $x$ and $y$ are both [-1, 1]? What ...
3
votes
1answer
314 views

NestList with a list inside?

I'm new to Mathematica, and was looking for more efficient ways to implement the Do loop below. a, ...
2
votes
1answer
157 views

User-defined Distance Functions with extra parameters [duplicate]

The Nearest function accepts a customized distance function. For example, a simple case that works well is ...
1
vote
1answer
82 views

Why is a function I defined in a package not visible when I load the package? [duplicate]

I made a package containing some functions in the following way. ...
6
votes
2answers
230 views

Not FullDefinition for Save. MachineID not Protected?

Is there a way to set what symbols's definitions I do not want to store? Consider the following code: ...
1
vote
1answer
220 views

Map a function conditional on elements at multiple relative positions in a list

I figure this question has many solutions, and if an answer already exists it would be nice just to be referred to it. I need a function that 'maps' over my list and produces a list of equal length ...
0
votes
1answer
62 views

Errors in evalauting an expression

I have the following: Constants: b3b = 2; G = (1/eps^2); a1 = 3; a3 = 4; xc = 0.3; Functions: ...
8
votes
3answers
237 views

How can I break through Function's HoldAll attribute to force evaluation of a body element?

The question concerns creating a function. Let consider the following code With[{f = Function[t, Cos[t]]}, {First[#], f'[#]} & ] which returns ...
4
votes
5answers
340 views

How to generalize and speed up this program?

There is a vector whose length is $n*m$, we can part it into $n$ sections in order. I want to define a function to compare the $i$-th and $i+1$-th section and find the minimum. The program for $n=m=3$ ...
1
vote
1answer
220 views

BSplinefunction and its derivative

Hi I am trying to use curve fit some data using the BSplinefunction. I havent been using Mathematica long, so my questions might be quite basic. ...
2
votes
1answer
256 views

How to compute a discrete histogram of a list [duplicate]

I'm trying to compute the discrete histogram of a set of values. By histogram I mean the absolute frequency a value appears on the dataset, by discrete I mean the values are from a discrete set, e.g. ...
0
votes
1answer
154 views

Understanding output of multivariable integration

I'm new to Mathematica and I'm trying to integrate this function: ...
0
votes
1answer
81 views

Scope of expression in a user-defined function

I have the following code: fbasic = A + R + Z*Z *Z*Z; f[A_, Z_, R_] := fbasic + R; f[0, 2, 3] The answer I am getting is ...
0
votes
1answer
184 views

Defining functions with changing number of variables [duplicate]

I am working with a bunch of functions of the form fn[x1_,x2_,x3_,...,xn_] := x1x2+x2x3+...+xnx1 where $n$ changes. Is there a way to create these functions ...
4
votes
4answers
229 views

How to avoid writing $K$ loops?

I want to evaluate a mathematical function of $K$ variables each of variables varying between 1:N. One way to do this is writing $K$ loops and varying variables accordingly, as shown below: ...
2
votes
4answers
227 views

Find time since last 0 in list

When I have a list of data (measured per day), is it possible to define a function that gives the nr of days since the data has been 0? I tried working with...
1
vote
1answer
220 views

Create continuous function from list

I have a list of data (measured per day) that I want to use as imput for another equation (say f). The problem is that the input I need for f needs to be a continuous function of time. Is it possible ...
2
votes
2answers
294 views

Writing a function that returns a (usable) function

I am trying to create a function that returns Arnold's Cat Map of size n iterated k times. I can get something out of the Function command, but I can't figure out ...
1
vote
4answers
207 views

How to use If to select arguments min & max in Range?

I want to call Range[] with its arguments depending on a condition. Say we have ...
0
votes
2answers
185 views

Inverse function

What probably could be the inverse of following function? ...
7
votes
2answers
506 views

How can I define a sequence of functions?

I need to define a function fun, and then re-define this function iteratively. The code is given at the end. First, a function ...
0
votes
0answers
66 views

Defining functions in a loop [duplicate]

I have a symbolic solution to a linear system with respect to some variables a[i,j] which depend on a parameter t. sol=Solve[...,Table[a[i,j],{i,0,n},{j,0,n}]] I ...
1
vote
0answers
219 views

Positive integrand giving negative answer

I'm integrating a positive function f(t) times sin(t) from 0 to pi/5 and get -38. Actually f is slightly negative for a short time (smallest value ~ -0.0005), but far from enough to explain this. ...
30
votes
4answers
521 views

How can the behavior of InterpolationOrder->0 be controlled?

In ListPlot and Interpolation, the option InterpolationOrder->0 uses two different ...