Last change
on this file since 392 was
378,
checked in by pinsard, 16 years ago
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improvements of headers (typo, links, paragraphes, etc)
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Property svn:eol-style set to
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Property svn:keywords set to
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File size:
1.2 KB
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1 | ;+ |
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2 | ; |
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3 | ; @file_comments |
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4 | ; find the union between 2 matrices of whole numbers |
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5 | ; |
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6 | ; see also <pro>different</pro> and <pro>inter</pro>. |
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7 | |
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8 | ; @categories |
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9 | ; Calculation |
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10 | ; |
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11 | ; @param a {in}{required} |
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12 | ; arrays of positive integers, which need |
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13 | ; not be sorted. Duplicate elements are ignored, as they have no |
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14 | ; effect on the result |
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15 | ; |
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16 | ; @param b {in}{required} |
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17 | ; see a |
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18 | ; |
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19 | ; @returns |
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20 | ; an array containing the set of values in a and b. |
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21 | ; |
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22 | ; @restrictions |
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23 | ; These functions will not be efficient on sparse sets with wide |
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24 | ; ranges, as they trade memory for efficiency. |
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25 | ; The <proidl>HISTOGRAM</proidl> function |
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26 | ; is used, which creates arrays of size equal to the range of the |
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27 | ; resulting set. |
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28 | ; |
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29 | ; @examples |
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30 | ; |
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31 | ; IDL> a = [2,4,6,8] |
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32 | ; IDL> b = [6,1,3,2] |
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33 | ; IDL> res=union(a,b) |
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34 | ; IDL> print, res |
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35 | ; 1 2 3 4 5 6 |
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36 | 8 |
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37 | ; this is the list ao all elements in either sets. |
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38 | ; |
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39 | ; @history |
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40 | ; <a href="http://www.dfanning.com/tips/set_operations.html"/> |
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41 | ; |
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42 | ; @version |
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43 | ; $Id$ |
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44 | ; |
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45 | ;- |
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46 | FUNCTION union, a, b |
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47 | ; |
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48 | compile_opt idl2, strictarrsubs |
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49 | ; |
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50 | IF a[0] LT 0 THEN RETURN, b ;A union NULL = a |
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51 | IF b[0] LT 0 THEN RETURN, a ;B union NULL = b |
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52 | RETURN, Where(Histogram([a,b], OMin = omin)) + omin ; Return combined set |
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53 | END |
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