1 | ;+ |
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2 | ; NAME: |
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3 | ; neighbor |
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4 | ; |
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5 | ; PURPOSE: |
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6 | ; find the closetest point of (P0) within a list of np1 points |
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7 | ; P1 Which can be on a sphere |
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8 | ; |
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9 | ; CATEGORY: |
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10 | ; Maps. |
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11 | ; |
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12 | ; CALLING SEQUENCE: |
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13 | ; Result = neighbor(lon0, lat0, lon1, lat1) |
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14 | ; |
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15 | ; INPUTS: |
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16 | ; Lon0, Lat0 = scalar. longitudes and latitudes of point P0. |
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17 | ; Lon1, Lat1 = np1 elements vector. longitude and latitude of |
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18 | ; np1 points P1 |
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19 | ; |
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20 | ; KEYWORD PARAMETERS: |
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21 | ; RADIANS = if set, inputs and angular outputs are in radians, otherwise |
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22 | ; degrees. |
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23 | ; DISTANCE = dis, to get back the distances between P0 and the np1 |
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24 | ; points P1 in the variable dis. |
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25 | ; /SPHERE to activate if points are located on a sphere. |
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26 | ; |
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27 | ; OUTPUTS: |
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28 | ; index giving the P1[index] point that is the closetest point |
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29 | ; of (P0) |
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30 | ; |
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31 | ; EXAMPLES: |
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32 | ; IDL> print, neighbor(-105.15,40.02,[-0.07,100,50],[51.30,20,0], $ |
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33 | ; distance=dis) |
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34 | ; 0 |
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35 | ; IDL> print, dis |
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36 | ; 105.684 206.125 160.228 |
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37 | ; |
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38 | ; MODIFICATION HISTORY: |
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39 | ; Sebastien Masson (smasson@lodyc.jussieu.fr) |
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40 | ; October 2003 |
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41 | ;- |
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42 | FUNCTION neighbor, p0lon, p0lat, neighlon, neighlat, sphere = sphere, distance = distance, radians = radians |
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43 | ; |
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44 | ; somme checks |
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45 | IF n_elements(p0lon) NE 1 THEN MESSAGE, 'Sorry p0lon must be a scalar' |
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46 | p0lon = p0lon[0] |
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47 | IF n_elements(p0lat) NE 1 THEN MESSAGE, 'Sorry p0lat must be a scalar' |
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48 | p0lat = p0lat[0] |
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49 | nneig = n_elements(neighlon) |
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50 | IF n_elements(neighlat) NE nneig THEN $ |
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51 | MESSAGE, 'neighlon and neighlat must have the same number of elements' |
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52 | ; distance between P0 and the others points |
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53 | IF keyword_set(sphere) THEN BEGIN |
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54 | IF sphere NE 1 THEN radius = sphere |
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55 | distance = Map_nPoints(p0lon, p0lat, neighlon, neighlat $ |
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56 | , radius = radius, radians = radians) |
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57 | ENDIF ELSE BEGIN |
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58 | distance = (neighlon-p0lon)^2+(neighlat-p0lat)^2 |
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59 | IF arg_present(distance) THEN distance = sqrt(distance) |
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60 | ENDELSE |
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61 | RETURN, where(distance EQ min(distance)) |
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62 | END |
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