Linked Questions

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Puzzling transformation rule output [duplicate]

My problem should be a trivial one but for the life of me I can't get it to work. This is my data (10 rows, each made up of a DateList and a list of 5 numeric values corresponding to that date); <...
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0answers
16 views

KeyAbsent when using Association in a replacement [duplicate]

I am trying to replace derivatives with other functions. I expected as = Association[fx -> dfx] Derivative[1][fx][x] /. Derivative[1][y_][_] -> as[y] to ...
1
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1answer
43 views

Replacing with Elements from a List [duplicate]

I have a fairly complicated expression with nested lists and I want to substitute a given string for each integer. Here's a simple example where ind is my integer-valued data structure and names is ...
2
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1answer
45 views

Why is the variable x not locally scope in the StringExpression?

Clear[x] StringCases["abcadcacb","a"~~x_~~"c"->x] {b,d} ...
1
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0answers
41 views

Replace date pattern [duplicate]

I have a list, such as the following: li = {"2017-10-16", 10.24, 10.71, 10.18, 10.61, 10.61, 16802200} Extracting the first element ...
0
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1answer
132 views

Sum of Sequence inside a replace rule? [duplicate]

I'd like a replacement rule that replaces derivatives with their total order. I tried ReplaceAll[Derivative[x__] -> Plus[x]][Derivative[1, 1]] but it doesn't ...
2
votes
1answer
99 views

Rule vs RuleDelayed in the context of StringReverse [duplicate]

{"test", 3} /. s_String :> StringReverse[s] {"test", 3} /. s_String -> StringReverse[s] The second line gives the error: StringReverse: String expected ...
1
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0answers
202 views

Problem in evaluating nested anonymous functions [duplicate]

It seems that I have found a bug (or a fundamental problem in the design of the programming language of Mathematica) with functions defined as rules. Define the function g as g(1)=2 and g(2)=1. We can ...
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0answers
20 views

How to define a function that utilizes the Range function? [duplicate]

How can I define a function that uses the Range function in its definition. A very simple example would be f[x_]=Range[x] However if I try that it outputs "Range ...
2
votes
1answer
88 views

how to manipulate pattern-matched lists for replacements

Consider the following simplified code snippet: line=Line[{#, 2 #} & /@ Range[10]] (* arbitrary line *) line /. {Line[x_List] -> Line[Most@x]} ...
0
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0answers
29 views

Replacement[] and Apply[], aren't commutative? [duplicate]

in my notebook, I have a function which output is of the kind: zzz[0,{a,b,c},{d,e,f,g},OptionsPattern] Then, I need to use this output in another form ...
0
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2answers
125 views

Merging two variables in one

I was looking for a way of, given two variables called A and B, obtaining a new variable called AB. My idea was doing simple pattern matching, e.g. ...
3
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1answer
182 views

Rule for derivatives

I have a differential equation of the form $$f'(x)=g(x,f(x))$$ (where $g$ is has a known explicit form, e.g. $x f(x)$) and I have an expression which contains several derivatives of $f$. I want to ...
2
votes
1answer
71 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] ...
2
votes
1answer
233 views

Confusion over blank sequence in pattern matching

My overall goal was to produce a list of heads used in a graphics output. For an example I used: ...

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