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| 5 | <title>grad.pro (SAXO Documentation Assistant)</title> |
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| 46 | <tr> |
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| 47 | <td width="10%"> |
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| 48 | <a href="div.html"><img src="./../prev.gif" border="0" alt="Previous"></a></td> |
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| 49 | <td width="80%" align="center" valign="center"> |
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| 50 | <font size=-1><i>SAXO Documentation Assistant</i>: <a href="./../home.html">Overview</a></font></td> |
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| 51 | <td width="10%" align="right"> |
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| 52 | <a href=""><img src="./../next.gif" border="0" alt="Next"></a></td> |
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| 53 | </tr> |
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| 54 | </table> |
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| 55 | |
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| 56 | |
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| 57 | <h1><font size="-2">Computation/</font></h1> |
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| 58 | <h2>grad.pro</h2> |
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| 59 | |
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| 60 | <dl> |
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| 61 | </dl> |
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| 62 | |
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| 63 | |
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| 64 | compute the gradient of a variable |
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| 65 | |
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| 66 | |
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| 67 | |
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| 68 | |
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| 69 | |
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| 70 | <a name="#_grad"></a> |
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| 71 | |
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| 72 | <h2>grad <font size="-1" color="#006633"> |
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| 73 | Calculation |
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| 74 | </font></h2> |
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| 75 | |
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| 76 | <p><font face="Courier"><i>result = </i>grad(<i><a href="#_grad_keyword_field">field</a>, <a href="#_grad_keyword_direc">direc</a></i>)</font></p> |
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| 77 | |
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| 78 | |
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| 79 | |
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| 80 | |
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| 81 | <h3>Return value</h3> |
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| 82 | the gradient of the input data with the same size 2D, 3D or 4D array |
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| 83 | |
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| 84 | |
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| 85 | |
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| 86 | <h3>Parameters</h3> |
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| 87 | |
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| 88 | |
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| 89 | <a name="#_grad_keyword_field"></a> |
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| 90 | <h4>field |
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| 91 | |
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| 92 | |
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| 93 | |
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| 94 | |
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| 95 | |
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| 96 | |
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| 97 | |
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| 98 | |
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| 99 | </h4> |
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| 100 | |
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| 101 | |
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| 102 | The field for which we want to compute the gradient. A 2D (xy), |
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| 103 | 3D (xyz or yt) or 4D (xyzt) array or a structure readable by |
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| 104 | <proidl>litchamp</proidl> |
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| 105 | and containing a 2D (xy), 3D (xyz or yt) or 4D (xyzt) array. |
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| 106 | Note that the dimension of the array must suit the domain dimension. |
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| 107 | |
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| 108 | |
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| 109 | |
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| 110 | <a name="#_grad_keyword_direc"></a> |
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| 111 | <h4>direc |
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| 112 | |
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| 113 | |
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| 114 | |
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| 115 | |
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| 116 | |
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| 117 | <font size="-1" color="#006633">type:</font> <font size="-1" color="#006633"><i>scalar string</i></font> |
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| 118 | |
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| 119 | |
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| 120 | </h4> |
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| 121 | |
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| 122 | |
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| 123 | the gradient direction: 'x', 'y', 'z' |
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| 124 | |
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| 125 | |
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| 126 | |
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| 127 | |
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| 128 | |
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| 129 | |
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| 130 | <h3>Examples</h3><pre> |
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| 131 | IDL> @tst_initorca2 |
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| 132 | IDL> plt, grad({arr:gphit,g:'T'}, 'x') |
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| 133 | IDL> plt, grad({arr:gphit,g:'T'}, 'y') |
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| 134 | |
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| 135 | </pre><h3>Version history</h3> |
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| 136 | |
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| 137 | <h4>Version</h4> |
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| 138 | $Id: grad.pro 238 2007-03-27 13:43:18Z pinsard $ |
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| 139 | |
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| 140 | <h4>History</h4> |
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| 141 | Sebastien Masson (smasson@lodyc.jussieu.fr) |
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| 142 | |
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| 143 | |
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| 144 | |
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| 145 | <h3>Known issues</h3> |
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| 146 | |
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| 147 | |
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| 148 | |
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| 149 | <h4>Restrictions</h4> |
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| 150 | - Works only for Arakawa C-grid. |
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| 151 | - When computing the gradient, the result is not on the same grid point |
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| 152 | than the input data. In consequence, we update, vargrid and the grid position |
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| 153 | parameters (firstx[tuvf], lastx[tuvf], nx[tuvf], firsty[tuvf], lasty[tuvf], |
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| 154 | ny[tuvf], firstz[tw], lastz[tw], nz[tw]). |
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| 155 | - points that cannot be computed (domain boundaries, coastline) are set to NaN |
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| 156 | - the common variable jpt is used to differ xyz (jpt=1) and xyt (jpt=1) cases. |
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| 157 | |
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| 158 | |
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| 159 | <h3>Other attributes</h3> |
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| 160 | |
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| 161 | |
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| 162 | <h4>Uses routines</h4> |
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| 163 | cm_4cal |
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| 164 | cm_4data |
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| 165 | cm_4mmesh |
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| 166 | |
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| 170 | |
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| 171 | <font size="-3"><p> </p></font> |
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| 172 | <hr size="1" color="#CCCCCC"/> |
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| 177 | <p><font color="gray" size="-3"> Produced by IDLdoc 2.0.</font></p> |
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| 178 | |
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| 179 | </body> |
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| 180 | </html> |
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