[2] | 1 | ;------------------------------------------------------------ |
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| 2 | ;------------------------------------------------------------ |
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| 3 | ;------------------------------------------------------------ |
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| 4 | ;+ |
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| 5 | ; NAME:union |
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| 6 | ; |
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| 7 | ; PURPOSE:calcule l''union de 2 matrices D'ENTIERS POSITIFS |
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| 8 | ; |
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| 9 | ; CATEGORY:calcule sur les matrices |
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| 10 | ; |
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| 11 | ; CALLING SEQUENCE:res=union(a,b) |
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| 12 | ; |
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| 13 | ; INPUTS:a et b:arrays of positive integers, which need |
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| 14 | ; not be sorted. Duplicate elements are ignored, as they have no |
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| 15 | ; effect on the result |
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| 16 | ; |
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| 17 | ; KEYWORD PARAMETERS: |
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| 18 | ; |
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| 19 | ; OUTPUTS:tableau |
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| 20 | ; |
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| 21 | ; COMMON BLOCKS: |
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| 22 | ; |
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| 23 | ; SIDE EFFECTS: |
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| 24 | ; |
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| 25 | ; The empty set is denoted by an array with the first element equal to |
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| 26 | ; -1. |
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| 27 | ; |
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| 28 | ; RESTRICTIONS: |
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| 29 | ; |
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| 30 | ; These functions will not be efficient on sparse sets with wide |
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| 31 | ; ranges, as they trade memory for efficiency. The HISTOGRAM function |
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| 32 | ; is used, which creates arrays of size equal to the range of the |
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| 33 | ; resulting set. |
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| 34 | ; |
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| 35 | ; EXAMPLE: |
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| 36 | ; |
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| 37 | ; a = [2,4,6,8] |
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| 38 | ; b = [6,1,3,2] |
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| 39 | ; union(a,b) = [ 1, 2, 3, 4, 6, 8] ; Elements in either set |
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| 40 | ; |
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| 41 | ; MODIFICATION HISTORY: |
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| 42 | ; |
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| 43 | ; http://www.dfanning.com/tips/set_operations.html |
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| 44 | ;- |
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| 45 | ;------------------------------------------------------------ |
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| 46 | ;------------------------------------------------------------ |
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| 47 | ;------------------------------------------------------------ |
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| 48 | FUNCTION union, a, b |
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[114] | 49 | ; |
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| 50 | compile_opt idl2, strictarrsubs |
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| 51 | ; |
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[2] | 52 | IF a[0] LT 0 THEN RETURN, b ;A union NULL = a |
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| 53 | IF b[0] LT 0 THEN RETURN, a ;B union NULL = b |
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| 54 | RETURN, Where(Histogram([a,b], OMin = omin)) + omin ; Return combined set |
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| 55 | END |
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