1 | ;+ |
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2 | ; |
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3 | ; @file_comments |
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4 | ;find the closetest point of (P0) within a list of np1 points |
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5 | ;P1 Which can be on a sphere |
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6 | ; |
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7 | ; @categories Maps |
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8 | ; |
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9 | ; @examples |
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10 | ; IDL> Result = neighbor(lon0, lat0, lon1, lat1) |
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11 | ; |
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12 | ;@param p0lon {in}{required} scalar. longitudes of point P0. |
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13 | ;@param p0lat {in}{required} scalar. latitudes of point P0. |
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14 | ; |
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15 | ; @keyword RADIANS if set, inputs and angular outputs are in radians, otherwise |
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16 | ;degrees. |
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17 | ; @keyword DISTANCE dis, to get back the distances between P0 and the np1 |
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18 | ; points P1 in the variable dis. |
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19 | ; @keyword /SPHERE to activate if points are located on a sphere. |
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20 | ; |
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21 | ; @returns |
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22 | ; index giving the P1[index] point that is the closetest point |
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23 | ; of (P0) |
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24 | ; |
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25 | ; @examples |
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26 | ; IDL> print, neighbor(-105.15,40.02,[-0.07,100,50],[51.30,20,0], $ |
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27 | ; distance=dis) |
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28 | ; 0 |
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29 | ; IDL> print, dis |
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30 | ; 105.684 206.125 160.228 |
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31 | ; |
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32 | ; @history |
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33 | ; Sebastien Masson (smasson\@lodyc.jussieu.fr) |
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34 | ; October 2003 |
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35 | ;- |
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36 | FUNCTION neighbor, p0lon, p0lat, neighlon, neighlat, sphere = sphere, distance = distance, radians = radians |
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37 | ; |
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38 | ; somme checks |
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39 | IF n_elements(p0lon) NE 1 THEN MESSAGE, 'Sorry p0lon must be a scalar' |
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40 | p0lon = p0lon[0] |
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41 | IF n_elements(p0lat) NE 1 THEN MESSAGE, 'Sorry p0lat must be a scalar' |
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42 | p0lat = p0lat[0] |
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43 | nneig = n_elements(neighlon) |
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44 | IF n_elements(neighlat) NE nneig THEN $ |
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45 | MESSAGE, 'neighlon and neighlat must have the same number of elements' |
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46 | ; distance between P0 and the others points |
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47 | IF keyword_set(sphere) THEN BEGIN |
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48 | IF sphere NE 1 THEN radius = sphere |
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49 | distance = Map_nPoints(p0lon, p0lat, neighlon, neighlat $ |
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50 | , radius = radius, radians = radians) |
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51 | ENDIF ELSE BEGIN |
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52 | distance = (neighlon-p0lon)^2+(neighlat-p0lat)^2 |
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53 | IF arg_present(distance) THEN distance = sqrt(distance) |
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54 | ENDELSE |
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55 | RETURN, where(distance EQ min(distance)) |
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56 | END |
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