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5 | <title>spl_keep_mean.pro (SAXO Documentation Assistant)</title> |
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45 | <table border="0" cellpadding="0" cellspacing="0" width="98%" bgcolor="#F0F0FF" valign="bottom"> |
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46 | <tr> |
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47 | <td width="10%"> |
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48 | <a href="spl_incr.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="square2quadrilateral.html"><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">Interpolation/</font></h1> |
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58 | <h2>spl_keep_mean.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 | Given the arrays X and Y, which tabulate a function (with the X[i] |
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65 | AND Y[i] in ascending order), and given an input value X2, the |
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66 | <a href="..//Interpolation/spl_incr.html">spl_incr</a> function returns an interpolated value for the given values |
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67 | of X2. The interpolation method is based on cubic spline, corrected |
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68 | in a way that integral of the interpolated values is the same as the |
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69 | integral of the input values. (-> for example to build daily data |
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70 | from monthly mean and keep the monthly mean of the computed daily |
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71 | data equal to the original values) |
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72 | |
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73 | |
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74 | |
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75 | |
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76 | |
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77 | <a name="#_spl_keep_mean"></a> |
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78 | |
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79 | <h2>spl_keep_mean </h2> |
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80 | |
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81 | <p><font face="Courier"><i>result = </i>spl_keep_mean(<i><a href="#_spl_keep_mean_keyword_x">x</a>, <a href="#_spl_keep_mean_keyword_yin">yin</a>, <a href="#_spl_keep_mean_keyword_x2">x2</a></i>, <a href="#_spl_keep_mean_keyword_YP0">YP0</a>=<i>YP0</i>, <a href="#_spl_keep_mean_keyword_YPN_1">YPN_1</a>=<i>YPN_1</i>, <a href="#_spl_keep_mean_keyword_GE0">GE0</a>=<i>GE0</i>)</font></p> |
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82 | |
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83 | |
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84 | |
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85 | |
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86 | <h3>Return value</h3> |
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87 | y2: the mean value between two consecutive values of x2. This |
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88 | array has one element less than y2. y2 has double precision. |
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89 | |
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90 | |
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91 | |
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92 | <h3>Parameters</h3> |
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93 | |
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94 | |
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95 | <a name="#_spl_keep_mean_keyword_x"></a> |
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96 | <h4>x |
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97 | <font size="-1" color="#006633">in</font> |
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98 | |
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99 | |
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100 | <font size="-1" color="#006633">required</font> |
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101 | |
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102 | |
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103 | |
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104 | |
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105 | </h4> |
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106 | |
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107 | |
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108 | An n-elements (at least 2) input vector that specifies the tabulate points in |
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109 | a strict ascending order. |
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110 | |
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111 | |
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112 | |
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113 | <a name="#_spl_keep_mean_keyword_yin"></a> |
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114 | <h4>yin |
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115 | <font size="-1" color="#006633">in</font> |
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116 | |
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117 | |
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118 | <font size="-1" color="#006633">required</font> |
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119 | |
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120 | <font size="-1" color="#006633">type:</font> <font size="-1" color="#006633"><i>array</i></font> |
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121 | |
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122 | |
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123 | </h4> |
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124 | |
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125 | |
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126 | an array with one element less than x. y[i] represents the |
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127 | mean value between x[i] and x[i+1]. if /GE0 is activated, y must |
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128 | have positive values. |
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129 | |
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130 | |
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131 | |
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132 | <a name="#_spl_keep_mean_keyword_x2"></a> |
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133 | <h4>x2 |
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134 | <font size="-1" color="#006633">in</font> |
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135 | |
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136 | |
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137 | <font size="-1" color="#006633">required</font> |
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138 | |
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139 | |
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140 | |
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141 | |
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142 | </h4> |
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143 | |
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144 | |
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145 | The input values for which the interpolated values are desired. |
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146 | Its values must be strictly monotonically increasing. |
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147 | |
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148 | |
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149 | |
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150 | |
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151 | |
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152 | <h3>Keywords</h3> |
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153 | |
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154 | |
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155 | <a name="#_spl_keep_mean_keyword_YP0"></a> |
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156 | <h4>YP0 |
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157 | |
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158 | |
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159 | |
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160 | |
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161 | |
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162 | |
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163 | |
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164 | |
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165 | </h4> |
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166 | |
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167 | |
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168 | The first derivative of the interpolating function at the |
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169 | point X0. If YP0 is omitted, the second derivative at the |
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170 | boundary is set to zero, resulting in a "natural spline." |
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171 | |
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172 | |
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173 | <a name="#_spl_keep_mean_keyword_YPN_1"></a> |
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174 | <h4>YPN_1 |
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175 | |
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176 | |
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177 | |
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178 | |
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179 | |
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180 | |
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181 | |
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182 | |
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183 | </h4> |
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184 | |
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185 | |
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186 | The first derivative of the interpolating function at the |
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187 | point Xn-1. If YPN_1 is omitted, the second derivative at the |
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188 | boundary is set to zero, resulting in a "natural spline." |
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189 | |
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190 | |
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191 | <a name="#_spl_keep_mean_keyword_GE0"></a> |
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192 | <h4>GE0 |
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193 | |
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194 | |
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195 | |
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196 | |
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197 | |
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198 | |
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199 | |
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200 | |
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201 | </h4> |
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202 | |
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203 | |
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204 | to force that y2 is always GE than 0. In that case, y must also be GE than 0. |
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205 | |
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206 | |
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207 | |
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208 | |
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209 | <h3>Examples</h3><pre> |
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210 | |
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211 | 12 monthly values of precipitations into daily values: |
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212 | |
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213 | IDL> yr1 = 1990 |
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214 | IDL> yr2 = 1992 |
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215 | IDL> nyr = yr2-yr1+1 |
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216 | IDL> n1 = 12*nyr+1 |
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217 | IDL> x = julday(1+findgen(n1), replicate(1, n1) $ |
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218 | IDL> , replicate(yr1, n1), fltarr(n1)) |
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219 | IDL> n2 = 365*nyr + total(leapyr(yr1+indgen(nyr))) + 1 |
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220 | IDL> x2 = julday(replicate(1, n2), 1+findgen(n2) $ |
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221 | IDL> , replicate(yr1, n2), fltarr(n2)) |
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222 | IDL> y = abs(randomn(0, n1-1)) |
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223 | IDL> y2 = spl_keep_mean(x, y, x2, /ge0) |
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224 | |
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225 | IDL> print, min(x, max = ma), ma |
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226 | IDL> print, min(x2, max = ma), ma |
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227 | IDL> print, vairdate([min(x, max = ma), ma]) |
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228 | IDL> print, total(y*(x[1:n1-1]-x[0:n1-2])) |
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229 | IDL> print, total(y2*(x2[1:n2-1]-x2[0:n2-2])) |
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230 | |
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231 | </pre><h3>Version history</h3> |
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232 | |
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233 | <h4>Version</h4> |
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234 | $Id: spl_keep_mean.pro 372 2008-08-08 12:31:53Z pinsard $ |
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235 | |
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236 | <h4>History</h4> |
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237 | Sebastien Masson (smasson@lodyc.jussieu.fr): May 2005 |
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238 | |
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239 | |
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240 | |
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241 | <h3>Known issues</h3> |
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242 | |
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243 | |
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244 | |
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245 | <h4>Restrictions</h4> |
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246 | It might be possible that y2 has very small negative values |
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247 | (amplitude smaller than 1.e-6)... |
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258 | <font size="-3"><p> </p></font> |
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259 | <hr size="1" color="#CCCCCC"/> |
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263 | |
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264 | <p><font color="gray" size="-3"> Produced by IDLdoc 2.0.</font></p> |
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265 | |
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266 | </body> |
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267 | </html> |
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