Indices: Difference between revisions
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<td>returns an integer vector identical to <apll>R/ | <td>returns an integer vector or nested vector of integer vectors identical to <apll>⊃,/,R/¨⊂¨⍳⍴1/R</apll>.</td> | ||
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<td><apll>R</apll> is | <td><apll>R</apll> is an array of non-negative integers.</td> | ||
</tr> | </tr> | ||
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<td><apll>Z</apll> is an integer vector of length <apll>+/R</apll> | <td><apll>Z</apll> is an integer vector of length <apll>+/,R</apll>.</td> | ||
</tr> | </tr> | ||
<tr> | <tr> | ||
<td> | <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> | ||
</tr> | |||
<tr> | |||
<td>For higher rank arrays, the result extends to produce a nested vector of vectors of the indices of all the positive integer elements of <apll>R</apll> replicated as per the corresponding value in <apll>R</apll>.</td> | |||
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0 2 3 4 6<br /> | 0 2 3 4 6<br /> | ||
⍸2 3 4<br /> | ⍸2 3 4<br /> | ||
0 0 1 1 1 2 2 2 2</apll> | 0 0 1 1 1 2 2 2 2<br /> | ||
⍸⎕←2 3⍴⍳4<br /> | |||
0 1 2<br /> | |||
3 0 1<br /> | |||
0 1 0 2 0 2 1 0 1 0 1 0 1 2<br /> | |||
⍸1 2 3⍴⍳4<br /> | |||
0 0 1 0 0 2 0 0 2 0 1 0 0 1 0 0 1 0 0 1 2<br /> | |||
<br /> | |||
∇ Z←(Txt Rep) txtrep Z;a<br /> | |||
[1] ⍝ Replace Txt in Z with Rep.<br /> | |||
[2] :Assert 2=⍴⍴Z ⋄ :Assert (⍴Txt)≡⍴Rep<br /> | |||
[3] a←⍸Txt⍷Z<br /> | |||
[4] Z[⊃⊃¨,¨/¨a+⊂0(0..¯1+⍴Txt)]←((⍴a),⍴Rep)⍴Rep<br /> | |||
∇<br /> | |||
'Now' 'Who' txtrep 4 13⍴'Now is the time...'<br /> | |||
Who is the ti<br /> | |||
me...Who is t<br /> | |||
he time...Who<br /> | |||
is the time.</apll> | |||
Revision as of 12:34, 30 October 2012
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| R is an array of non-negative integers. | ||||
| Z is an integer vector of length +/,R. | ||||
| For scalars or vectors, the result is equivalent to R/⍳⍴1/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. |
For example, in origin-0
⍸1 0 1 1 1 0 1
0 2 3 4 6
⍸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.
