Questions tagged [head]
The head tag has no usage guidance.
38
questions
5
votes
1
answer
172
views
Why is Around omitted when the uncertainty is zero?
I have a list of values with errors and I use Around[x, dx]. Some of those values have an error of zero though. Mathematica removes the ...
- 53
6
votes
1
answer
302
views
A problem on the pattern (:) of Heads
I defined
Clear[f, g]
f[(h : Exp | Log)[x_]] := x;
g[(h : Log | Exp)[x_]] := x;
The code gives a weird result:
...
- 193
11
votes
2
answers
467
views
How can I create an atomic head or treat some head as atomic during Map?
For example,
Map[g, {0, {h[1, 2, 3]}}, {-1}]
gives
{g[0], {h[g[1], g[2], g[3]]}}
I want a ...
- 17k
2
votes
0
answers
53
views
When should I use Audio vs Sound Data types?
It seems like mathematica has 2 related data types Audio and sound.
Why is there 2 separate data types? When would I use one versus the other?
Guesses
I know I can convert between them by ...
- 761
2
votes
0
answers
41
views
Can't match custom head in function signature [closed]
I have written a financial charting function which has the following signature;
...
- 790
0
votes
1
answer
67
views
any way to store the values of the controls of a Manipulate so that one can reuse them in the future excutions
I’m using Manipulate[] to adjust several parameters, which will eventually generate some figures. After I get the desired view, I’d like to store the set of control parameters so that I can reuse them ...
- 695
4
votes
2
answers
245
views
How many @ need to be used when I try to use apply function? [closed]
According to the manual, $f@@A$ means apply function $f$ to $A$. If it would be the same if I only use one @? Does $f@A$ still represent apply apply function $f$ to $A$? And it would help a lot if ...
- 107
5
votes
1
answer
124
views
Extracting n-th part of an expression without any evaluation
Is it possible to extract n-th part of an expression as a string, without any evaluation?
For example,
...
- 4,047
18
votes
1
answer
376
views
Head[x] vs x[[0]]
Can we say Head[x] and x[[0]] are identical ?
In mathematica manual I could find : 'The head is the part with index 0'
But I am not sure whether Head[x] are x[[0]] are really interchangeable in any ...
- 4,047
2
votes
2
answers
94
views
Understanding f /@ g[x,y,z] [closed]
According to the Mathematica guide,
In[26]:= f /@ g[x, y, z]
Out[26]= g[f[x], f[y], f[z]]
In a simple example, this works as desired with symbolic values:
...
- 143
1
vote
1
answer
119
views
How to use column header as the x-axis in ListPlot?
I imported a csv file, and the header of the columns are specific dates. How would I plot these points using ListPlot, but the x-axis instead of 1,2,3, etc, is the dates from the column headers?
For ...
- 31
1
vote
1
answer
100
views
Dropping curly brackets from a list [closed]
I would like to make many plots using the same plot parameters. I am trying to define a plot parameter list such as
...
- 11
4
votes
1
answer
76
views
Name of patterns cast as expressions from strings
I'm trying to match a part of a string while imposing conditions on the patterns, e.g.:
StringCases["223", a: DigitCharacter ~~ b: DigitCharacter /; Unequal[a, b]]
...
- 483
0
votes
1
answer
75
views
Count heads: e.g. neglect all terms $\sin(x) \sin (y) \sin (z) \sin (w)$ for all values of the argument
I have a polynomial (functional) expression $E[F]$ in terms of a function $F$.
I want to take an $F$-cube truncation in the sense that I want to and make terms of the form $F[w]F[x]F[y]F[z]$ vanish ...
- 155
-1
votes
1
answer
76
views
Function matching any head (Example: h_[_,_] := 5)
I want to define a function matching any expression with 2 parameters. For example:
_[_, _] := 5
I get the following error:
SetDelayed::nosym: "[,_] does not ...
- 51
3
votes
4
answers
388
views
How to remove style from a styled number?
For example, I have a number with style like so:
Style[1, Red, 20]
How do I remove its style, so it returns to its inner value 1...
- 589
13
votes
7
answers
808
views
Getting the "root" Head
I have a dynamic list of function names, like {f1, f2, f3, ...}, and they will enter in computation in various forms ...
- 513
1
vote
1
answer
11
views
Parsing the link returned by CloudExport
Consider
Is there a way to make a function justLink that parses a CloudObject[<link>] and returns just the string ...
- 3,115
3
votes
2
answers
179
views
Extracting terms with certain heads in a function
Given a function with several arguments
func[a,b,g1[x],g1[x,y],g2[1],g2[g1[1]],3]
I would like to extract all arguments with the head ...
- 591
8
votes
1
answer
200
views
Why does MatchQ[a, r_ /; Head[r] != Plus] evaluate to False?
I'm trying to understand. Why is it that:
MatchQ[a, r_ /; Head[r] != Plus]
Evaluates to:
False
? For me, I would think ...
- 1,427
26
votes
2
answers
3k
views
Why no RationalQ or RealQ?
Interesting pattern came up as I go through the homework replies of my students. Why is there no RationalQ or RealQ? We have <...
- 3,912
4
votes
1
answer
376
views
Testing Head inside a Module [closed]
I hava a Module in which a want to give a single String or a List as a parameter and I want to change a single String to a List containing this String. So I did the ...
- 5,573
4
votes
1
answer
206
views
question about using Heads->True in Cases command
I was trying to find the order of highest derivative of expression. Using solution given in detect-highest-order-of-derivative-in-expression
I just do not understand why when removing ...
- 137k
1
vote
2
answers
1k
views
Head replacement [duplicate]
Input Code
a[1]=UnitVector[4,1]
b[1]=1
Now I want replace the head of b[1] by a, ...
- 355
5
votes
1
answer
114
views
How to obtain a list of all build-in system level Heads?
I am writing a small Mathematical expression parser and need a list of all Mathematica build-in Heads (system context?) so I can check the type of input.
Such as ...
- 137k
8
votes
2
answers
235
views
Replace Complex Head with List
I would like to apply ListPlot to a set of complex numbers. This is what comes to mind to convert a complex number to a pair:
...
- 183
2
votes
1
answer
120
views
Gather element of a list based on their head
I have list of the form
{y[-1], y[0], w'[1], y'[0], w'''[-1], z''[-1]}
and I would like to gather the elements together based on their heads to have
...
- 463
3
votes
1
answer
619
views
How can I replace a head on a specific level?
So in my notebook I have a list of long expressions which are sums of a bunch of terms. I would like to look at each of these terms individually and try to remove them based on some criteria. My idea ...
- 33
1
vote
1
answer
1k
views
How to "invert" a rule
The subject is a bit cryptic, I know, but here is what I'd like to do: Let's say I am solving an ODE like this:
...
- 4,129
7
votes
2
answers
343
views
How to access Dataset's metadata
A Dataset object has internal metadata. For example, let
ds = Dataset[{<|"a" -> 1, "b" -> "x", "c" -> {1}|>}];
...
- 11.7k
2
votes
1
answer
85
views
Why is head evaluation inconsistent in pattern replacement?
I noticed the following unexpected result:
In[90]:= "foo" /. x_String -> Head[x]
Out[90]= Symbol
Why is it that Head[x] ...
- 377
5
votes
1
answer
331
views
How to represent 1 as Symbol["Integer"]
Maybe this is a boring question, but I cannot figure it out. Because every expression has a Head, and Head[1] is ...
- 2,541
6
votes
1
answer
434
views
How to Collect a variable multiplied by a constant?
I'd like to use Collect to get terms that have a variable multiplied by a constant. For example I'd like:
Collect[x + b x, b x]
...
- 1,870
4
votes
1
answer
993
views
What is the definition of head in Mathematica? [closed]
I know (by practice) what a head is, but I am unable to find the appropriate words to actually define it. I would like to see a precise definition of head using the appropriate technical words ...
user34309
1
vote
1
answer
225
views
Why does the Derivative function not appear in the tree form? [closed]
I was learning that set delay doesn't evaluate things until its calling time. Hence, I thought that something like the followng:
dfdt := D[f[t],t]
would not ...
- 265
6
votes
2
answers
679
views
Is there any way to use head of Real and Integer altogether?
Is there any way to use the head of Integer and Real together like below?
The below is not right, I know that, it is just for ...
- 497
2
votes
0
answers
378
views
Custom Head for Encapsulation
Often when I'm writing a project in Mathematica, the number of arguments I must provide to functions spins out of control.
I need a sort of object-oriented encapsulation approach. I've already had a ...
- 1,089
6
votes
1
answer
1k
views
Pattern matching list of elements with different heads
I have a function, which I want to accept only a list of kind of elements belonging to a group. The task comes down to finding an elegant pattern suitable for easy to read function prototype.
As an ...
- 4,876