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Last change
on this file since 2 was
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checked in by opalod, 22 years ago
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Initial revision
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Property svn:eol-style set to
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Author Date Id Revision
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File size:
833 bytes
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| 1 | ;+ |
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| 2 | ; NAME: |
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| 3 | ; |
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| 4 | ; ROTATION |
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| 5 | ; |
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| 6 | ; PURPOSE: |
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| 7 | ; |
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| 8 | ; Rotate two vectors by a specified amount. |
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| 9 | ; |
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| 10 | ; CALLING SEQUENCE: |
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| 11 | ; |
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| 12 | ; ROTATION,X,Y,DEG,NX,NY |
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| 13 | ; |
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| 14 | ; INPUTS: |
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| 15 | ; |
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| 16 | ; X,Y :orignal data point pairs |
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| 17 | ; |
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| 18 | ; DEG :degrees to rotate. |
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| 19 | ; |
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| 20 | ; OUTPUTS: |
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| 21 | ; |
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| 22 | ; Nx, Ny = rotated point pairs. |
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| 23 | ; |
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| 24 | ; MODIFICATION HISTORY: |
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| 25 | ; |
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| 26 | ; Jeff Bennett, U of Colorado |
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| 27 | ;- |
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| 28 | |
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| 29 | PRO ROTATION,X,Y,DEG,NX,NY |
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| 30 | ang=deg*!dtor |
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| 31 | |
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| 32 | ;convert to polar coordinates for rotation |
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| 33 | r = sqrt(x*x + y*y) |
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| 34 | theta = r*0. |
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| 35 | ;get angle in for loop so that zero radii will be left as zero angle |
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| 36 | for i = 0,n_elements(r)-1 do $ |
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| 37 | if r(i) ne 0 then theta(i) = atan(y(i),x(i)) ;range from -pi to +pi |
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| 38 | ; |
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| 39 | ;add rotation angle |
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| 40 | theta = theta + ang |
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| 41 | ; |
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| 42 | ;convert back to rectangular coordinates, now rotated |
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| 43 | nx = r * cos(theta) |
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| 44 | ny = r * sin(theta) |
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| 45 | ; |
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| 46 | return |
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| 47 | end |
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