Questions tagged [pure-function]
Questions about implementing or applying functions which: (1) always yield the same result for the same input, (2) are independent of outside information, and (3) produce no side effects.
244
questions
1
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1
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79
views
A way to generalize my code for this non linear ODE problem
I am trying to solve the differential equation $y''(x) = y(x)+\sin[y'(x)]$ using "Fixed Point Iteration" over the interval $[0,1].$ Now using central difference method I arrived at the ...
- 143
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vote
0
answers
65
views
Mapping two pure functions over different lists
Say if I have two lists of vectors of the same length, for example:
u = {{1,0,0},{0,1,0},{0,0,1}}
v = {{1,0,1},{1,1,0},{1,1,1}}
I want to add (modulo 2) ...
- 417
1
vote
0
answers
71
views
Why must the "&" symbol be placed inside function instead of outside? [closed]
The following code is taken from Wolfram Community "Quantum Error Correction: bit flip".
...
- 417
2
votes
0
answers
33
views
Use FoldList to successively ImageAdd regular polygons with between 3 and 8 sides, and with opacity 0.2 [closed]
This question is from Section 29 of "An Elementary Introduction to the Wolfram Language".
The objective is to successively add regular polygons with between 3 and 8 sides, and with opacity 0....
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2
votes
0
answers
71
views
Memory leak with pure function and in the listable option of compiled function?
I'm using
13.0.0 for Microsoft Windows (64-bit) (December 3, 2021)
When I repeatedly run the command
...
- 341
5
votes
1
answer
228
views
Pure functions: currying for & notation
I looked up currying in Shifrin's book.
He points out that currying can be used for pure functions using nested functions as in the following example:
...
- 1,596
3
votes
1
answer
82
views
Condition inside pure function
Why condition /; not work inside pure function?
Suppose we have:
...
- 1,085
3
votes
1
answer
69
views
Pure function with pattern test
Is it possible to achieve pattern test inside a pure function?
I have tried
f = Function[{x_?NumericQ},
x
]
but the error Function::flpar occured.
- 151
10
votes
5
answers
1k
views
Pure function of lists
I need to create a function with two arguments f(s, l):
s is a list of three integer like:
s={1,-3,+5}
and l is a list of lists of naturals of same length:
...
- 477
3
votes
1
answer
189
views
Pure functions failing in algebra
f[equation_] := Module[{},
ContourPlot[equation[x, y] == 1, {x, -2, 2}, {y, -2, 2}]
]
equation = (#1^2 + #2^2) &;
f[equation]
The above code draws a circle....
- 229
3
votes
1
answer
81
views
How to define pure functions in matrix form?
I want to define pure functions x(#1,#2) and y(#1,#2) like
But they aren't proper pure functions in the current form. How to modify the code?
- 229
7
votes
2
answers
466
views
Pure function on pure function
Given
t1 = {2, 4, 8, 16};
t2 = {1, 5, 9};
First[Select[t1, # > 1 &]]
First[Select[t1, # > 5 &]]
First[Select[t1, # > 9 &]]
can somehow be ...
- 2,304
4
votes
2
answers
150
views
Slots inside nested pure functions
I'd like /@ instead of Table or Map.
But let we have it inside pure function:
...
- 1,085
3
votes
3
answers
72
views
Sort a list using a scoring list with Switch [duplicate]
I have a minimal working example (MWE) list called listToSort that is a list of string triplets:
...
- 10.2k
0
votes
1
answer
51
views
Sorting a list by increasing order algorythm [closed]
Im new to loops on mathematica,was wondering how could I create a function to loop through a list which finds the index of the smallest value of that list, makes a sublist from index 1 to that ...
- 93
1
vote
1
answer
80
views
Drawing lines between coordinates in a list
Variable "l" is a list of coordinates and I am trying to draw a line from each coordinate to the next. But how? Apparently the last line isn't working.
...
- 2,311
3
votes
1
answer
81
views
MapAt with pure functions
Consider
expr = Hold[1 + a + x + b + c + y + z];
idxes = {{1, 3}, {1, 4}};
Q1. I don't understand why
...
- 572
4
votes
3
answers
573
views
Can a pure function be constructed whose argument list is a matrix?
Can a pure function be constructed whose argument list is a matrix?
Using Function, I know it's not possible, but I'd like to get something like:
...
- 11.4k
5
votes
5
answers
1k
views
How to simplify a pure function?
I am dealing with the vibration of a multi degree of freedom system with driving force, and I need to find the relation between the amplitude and the frequency of the driving force.
I hope to get an ...
- 328
1
vote
2
answers
101
views
Nested pure function argument as table
I made a nested pure function
Nest[(x^2)/ ((2x+1) + #)&, x,n]
I would like that for each iteration the value of x increment of 1, to have something like
$$\...
- 83
3
votes
1
answer
154
views
How to replace a multiple iterator Table to speed up computation
I need to create an array of data which resembles to something like this
Table[{i, Sin[j^2*i]}, {j, 2000}, {i, 0., Pi, Pi/10000.}]
where each "row" of ...
- 953
0
votes
0
answers
21
views
How to select from a sum the terms containing minus? [duplicate]
In a sum
y = \[Beta] x v - \[Mu] y z - \[Gamma] y;
I would like to extract the terms which contain a minus, i.e. - [Mu] y z and - [Gamma] y
I can test when a term ...
- 1,582
2
votes
1
answer
126
views
Minimize Sum of Hamming Distances
Problem:
Given an $n \times m$ matrix with binary values $(0,1)$, find a binary vector that minimizes the sum of Hamming Distances to the rows.
Example:
If the matrix is {{$1,1,1$},{$0,0,0$},{$1,0,1$}}...
- 35
28
votes
1
answer
937
views
When is ##@@@##& more appropriate than ##@@##&?
When assigning attachment operators, I often run into confusing statements like ##@@##&, ##@@@##&, or even ...
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9
votes
4
answers
449
views
Construct a pure function containing built-in 'Sequence'
I guessed the output for
(Sequence[#, 7]&)[3]
should be
Sequence[3,7]
But my guess was wrong. See the screenshot:
And I ...
- 4,037
0
votes
2
answers
124
views
Spurious renaming in nested Function construct
From the documentation of Function, I take this example (slightly simplified). Renaming the dummy or bound variable (y->y$ in the inner ...
- 879
5
votes
1
answer
64
views
Splitting a list into sublists at provided markers
For a list of strings (or other elements):
SeedRandom[3];
t1 = Table[RandomChoice[CharacterRange["A", "E"]], 20]
...
- 37.8k
2
votes
2
answers
133
views
Evaluating a FittedModel over a list of values
Simplified version
Using the simpler version suggested by @ulrich-neumann :
...
- 23
3
votes
1
answer
117
views
Why do these two calls to Apply return different results?
In the following example, why do these two calls to Apply return different results?
...
- 10.2k
7
votes
5
answers
477
views
An anonymous function with constraints [duplicate]
I'm not very good at working with anonymous functions, a fact that has now come back to bite me. Suppose I have a function defined as follows:
...
- 346
0
votes
1
answer
50
views
MeshFunctions::invmeshf that resists other solutions
I'm trying to base mesh on the slope of the function. That's why there is a Cross of two partial derivatives.
...
- 145
4
votes
1
answer
92
views
Apply function modification to curried function
This is based on A function that modifies functions - well-defined operation?, a previous question of mine.
Lukas Lang's answer of course works very well, but now I encountered the following edge case:...
- 175
8
votes
1
answer
310
views
How to supply argument to pure function when slot is already defined?
Here's an example of a pure function:
3^# > 100 &
I can supply any value I please to the function, by placing that value after the prefix. E.g.:
...
- 3,548
0
votes
0
answers
47
views
Why does this function only work with exact numbers?
First, I tried calculating A^k with this and got an error.
...
- 2,361
0
votes
3
answers
141
views
How to use a pure function to write following sum?
How to use a pure function to write following sum?
I have tried to use FoldList, but it is still not working.
- 11
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votes
1
answer
56
views
Maximize returns unevaluated even though there is a global maximum
I was trying to calculate the maximum of a gaussian plus a line, but Maximize return unevaluated:
...
- 31
5
votes
2
answers
161
views
bind specific 'Slots' to specific 'Map'
Is it possible to construct a pure function using multiple slots, with the following concept :
Binding specific slot to specific apply or map
For example :
In this example,
To ...
- 4,037
1
vote
1
answer
114
views
pure function assignment
I do not understand this statement from the Introduction to Dynamic tutorial:
...
- 11
1
vote
1
answer
61
views
Apply function using level
The following use of Level is documented, without any example.
Let's try some simple codes :
...
- 4,037
0
votes
0
answers
119
views
Numerical errors in compiled function involving real and complex numbers as output
I am trying to use the Compile command in Mathematica to reduce the computation time because of its fast execution within Mathematica and ability to use the ...
- 13
5
votes
1
answer
148
views
Reduce from two pure functions to one
Liking the headings and spacing allowed by Row[] and TableForm[]
I set up the below with 3 TableForm[]'s to use as a model from which to
generalize, using a pure function, to display a list of 3-ples, ...
- 624
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vote
0
answers
69
views
Shorten Pure Function
My task is to write a pure function with 5 characters or less that can be called with a single number a or a list {a,b,c} and returns 1/a^3 or {1/a^3,1/b^3, 1/c^3,...}, depending on the input. I am ...
- 89
0
votes
0
answers
25
views
Pure functions with derivatives and list elements [duplicate]
I have a list
list = {x, y, z}
and then the following line
D[#, list[[2]]] &
gives the output
...
- 283
6
votes
1
answer
151
views
Using a pure function as an option of a function
Here's my code:
Options[f] = {"Func" -> Exp};
f[x_, OptionsPattern[]] := OptionValue["Func"][x]
f[2, "Func" -> (# + 2) &]
...
- 159
4
votes
0
answers
45
views
`Function` does something bizarre with formal parameters
I think this may overlap with existing questions, including one I asked years ago, but I'm not sure how, because the behavior I'm seeing is confusing enough I can't even really describe it except to ...
- 18.2k
5
votes
3
answers
192
views
Function incorrectly renaming variables in Rule Pattern
Consider the simple pure Function containing a Rule with the named pattern q.
...
- 1,151
0
votes
1
answer
70
views
How to write a function returning Chebyshev Polynominals of the first kind using Nest[]? [duplicate]
I want to create a function returning the Chebyshev polynomials of the first kind using the in build Nest[] function, preferably with a pure function.
I know there exist an in-build function for the ...
1
vote
2
answers
201
views
Pattern matching tuples as inputs to pure function
I've been having an issue with functions which are supposed to receive as input a list of tuples.
My troubles are two-fold:
The function doesn't properly identify the pattern test I laid out in the ...
- 21
0
votes
1
answer
72
views
Dot product two lists containing pure functions
Can i get something like this to work?
{D[#1, t] & , D[#1, x] & } . {t, y}
and my expected output be
...
- 576
1
vote
2
answers
163
views
How to flip the function f(x) about y-axis
Suppose I have a function W(x). I wanted to flip (reflect) this function about the y-axis. I tried plotting W(-x) but it is not ...
- 1,699