Difference between revisions of "Indices"

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       <td>returns a simple integer vector or nested vector of integer vectors identical to <apll>(,R)/,⍳⍴1/R</apll>.</td>
+
       <td>returns a simple integer vector or nested vector of integer vectors identical to <apll>(,R)/,⍳⍴R</apll>.</td>
 
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   <td><apll>Z</apll> is an integer vector of length <apll>+/,R</apll>.</td>
+
   <td>For vector <apll>R</apll>, <apll>Z</apll> is an integer vector.  For all other ranks of <apll>R</apll>, <apll>Z</apll> is a nested vector of integer vectors.  In both case the length of <apll>Z</apll> is <apll>+/,R</apll>.</td>
 
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   <td>For scalars or vectors, the result is equivalent to <apll>R/⍳⍴1/R</apll> which encapsulates a very common idiom in one symbol.</td>
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   <td>For scalars or vectors, the result is equivalent to <apll>R/⍳⍴R</apll> which encapsulates a very common idiom in one symbol.</td>
 
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<p>For example, in origin-0</p>
 
<p>For example, in origin-0</p>
  
<apll>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⍸3<br />
+
<apll>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⍸,3<br />
 
0 0 0<br />
 
0 0 0<br />
 +
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⍬⍬⍬≡⍸3 ⍝ for scalar S, ⍸S ←→ S⍴⊂⍬  as per the definition R/⍳⍴R<br />
 +
1<br />
 +
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⍬≡⍸⍬<br />
 +
1<br />
 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⍸1 0 1 1 1 0 1<br />
 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⍸1 0 1 1 1 0 1<br />
 
0 2 3 4 6<br />
 
0 2 3 4 6<br />

Revision as of 23:43, 4 February 2018

Z←⍸R returns a simple integer vector or nested vector of integer vectors identical to (,R)/,⍳⍴R.
R is a simple array of non-negative integers.
For vector R, Z is an integer vector. For all other ranks of R, Z is a nested vector of integer vectors. In both case the length of Z is +/,R.
For scalars or vectors, the result is equivalent to R/⍳⍴R which encapsulates a very common idiom in one symbol.
For higher rank arrays, the result extends to produce a nested vector of vectors of the indices of all the positive integer elements of R replicated as per the corresponding value in R.
This function is sensitive to ⎕IO.


For example, in origin-0

      ⍸,3
0 0 0
      ⍬⍬⍬≡⍸3 ⍝ for scalar S, ⍸S ←→ S⍴⊂⍬ as per the definition R/⍳⍴R
1
      ⍬≡⍸⍬
1
      ⍸1 0 1 1 1 0 1
0 2 3 4 6
      ⍸'Now is the time'=' '
3 6 10
      ⍸2 3 4
0 0 1 1 1 2 2 2 2
      ⍸⎕←2 3⍴⍳4
 0 1 2
 3 0 1
 0 1  0 2  0 2  1 0  1 0  1 0  1 2
      ⍸1 2 3⍴⍳4
 0 0 1  0 0 2  0 0 2  0 1 0  0 1 0  0 1 0  0 1 2

    ∇ Z←(Txt Rep) txtrep Z;a
[1]   ⍝ Replace Txt in Z with Rep.
[2]   :Assert 2=⍴⍴Z ⋄ :Assert (⍴Txt)≡⍴Rep
[3]   a←⍸Txt⍷Z
[4]   Z[⊃⊃¨,¨/¨a+⊂0(0..¯1+⍴Txt)]←((⍴a),⍴Rep)⍴Rep
    ∇
      'Now' 'Who' txtrep 4 13⍴'Now is the time...'
Who is the ti
me...Who is t
he time...Who
 is the time.