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| 81 | <h1 class="directory"><a href="directory-overview.html?format=raw">Interpolation/</a></h1> |
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| 82 | <h2 class="pro_file">spl_keep_mean.pro</h2> |
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| 99 | <div id="routine_details"> |
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| 100 | |
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| 101 | |
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| 102 | <div class="routine_details" id="_spl_keep_mean"> |
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| 103 | |
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| 104 | <h2><a class="top" href="#container">top</a>spl_keep_mean </h2> |
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| 105 | |
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| 106 | <p class="header"> |
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| 107 | <span class="result">result = </span>spl_keep_mean(<span class="result"><a href="#_spl_keep_mean_param_x">x</a>, <a href="#_spl_keep_mean_param_yin">yin</a>, <a href="#_spl_keep_mean_param_x2">x2</a></span>, <a href="#_spl_keep_mean_keyword_YP0">YP0</a>=<span class="result">YP0</span>, <a href="#_spl_keep_mean_keyword_YPN_1">YPN_1</a>=<span class="result">YPN_1</span>, <a href="#_spl_keep_mean_keyword_GE0">GE0</a>=<span class="result">GE0</span>)</p> |
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| 108 | |
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| 109 | <div class="comments"> |
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| 110 | NAME:spl_keep_mean |
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| 111 | |
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| 112 | PURPOSE: |
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| 113 | |
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| 114 | Given the arrays X and Y, which tabulate a function (with the X[i] |
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| 115 | AND Y[i] in ascending order), and given an input value X2, the |
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| 116 | SPL_INCR function returns an interpolated value for the given values |
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| 117 | of X2. The interpolation method is based on cubic spline, corrected |
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| 118 | in a way that integral of the interpolated values is the same as the |
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| 119 | integral of the input values. (-> for exemple to build daily data |
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| 120 | from monthly mean and keep the monthly mean of the computed daily |
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| 121 | data equa to the original values) |
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| 122 | |
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| 123 | CATEGORY: |
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| 124 | |
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| 125 | CALLING SEQUENCE: y2 = spl_keep_mean(x, y, x2) |
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| 126 | |
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| 127 | INPUTS: |
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| 128 | |
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| 129 | x: An n-element (at least 2) input vector that specifies the |
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| 130 | tabulate points in a strict ascending order. |
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| 131 | |
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| 132 | y: an array with one element less than x. y[i] represents the |
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| 133 | mean value between x[i] and x[i+1]. if /GE0 is activated, y must |
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| 134 | have positive values. |
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| 135 | |
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| 136 | x2: The input values for which the interpolated values are |
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| 137 | desired. Its values must be strictly monotonically increasing. |
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| 138 | |
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| 139 | KEYWORD PARAMETERS: |
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| 140 | |
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| 141 | /GE0: to force that y2 is always GE than 0. In that case, y must |
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| 142 | also be GE than 0. |
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| 143 | |
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| 144 | YP0: The first derivative of the interpolating function at the |
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| 145 | point X0. If YP0 is omitted, the second derivative at the |
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| 146 | boundary is set to zero, resulting in a "natural spline." |
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| 147 | |
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| 148 | YPN_1: The first derivative of the interpolating function at the |
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| 149 | point Xn-1. If YPN_1 is omitted, the second derivative at the |
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| 150 | boundary is set to zero, resulting in a "natural spline." |
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| 151 | |
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| 152 | OUTPUTS: |
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| 153 | |
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| 154 | y2: the meean value between two consecutive values of x2. This |
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| 155 | array has one element less than y2. y2 has double precision. |
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| 156 | |
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| 157 | COMMON BLOCKS: none |
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| 158 | |
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| 159 | SIDE EFFECTS: ? |
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| 160 | |
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| 161 | RESTRICTIONS: |
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| 162 | It might be possible that y2 has very small negative values |
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| 163 | (amplitude smaller than 1.e-6)... |
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| 164 | |
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| 165 | |
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| 166 | EXAMPLE: |
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| 167 | |
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| 168 | 12 monthly values of precipitations into daily values: |
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| 169 | |
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| 170 | yr1 = 1990 |
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| 171 | yr2 = 1992 |
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| 172 | nyr = yr2-yr1+1 |
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| 173 | n1 = 12*nyr+1 |
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| 174 | x = julday(1+findgen(n1), replicate(1, n1) $ |
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| 175 | , replicate(yr1, n1), fltarr(n1)) |
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| 176 | n2 = 365*nyr + total(leapyr(yr1+indgen(nyr))) + 1 |
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| 177 | x2 = julday(replicate(1, n2), 1+findgen(n2) $ |
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| 178 | , replicate(yr1, n2), fltarr(n2)) |
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| 179 | y = abs(randomn(0, n1-1)) |
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| 180 | y2 = spl_keep_mean(x, y, x2, /ge0) |
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| 181 | |
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| 182 | print, min(x, max = ma), ma |
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| 183 | print, min(x2, max = ma), ma |
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| 184 | print, vairdate([min(x, max = ma), ma]) |
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| 185 | print, total(y*(x[1:n1-1]-x[0:n1-2])) |
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| 186 | print, total(y2*(x2[1:n2-1]-x2[0:n2-2])) |
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| 187 | |
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| 188 | MODIFICATION HISTORY:</div> |
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| 189 | |
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| 190 | |
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| 191 | |
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| 192 | |
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| 193 | <h3>Parameters</h3> |
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| 194 | |
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| 195 | |
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| 196 | <h4 id="_spl_keep_mean_param_x">x |
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| 197 | |
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| 204 | |
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| 205 | </h4> |
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| 206 | |
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| 207 | <div class="comments"></div> |
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| 208 | |
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| 209 | <h4 id="_spl_keep_mean_param_yin">yin |
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| 217 | |
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| 218 | </h4> |
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| 219 | |
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| 220 | <div class="comments"></div> |
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| 221 | |
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| 222 | <h4 id="_spl_keep_mean_param_x2">x2 |
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| 231 | </h4> |
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| 232 | |
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| 233 | <div class="comments"></div> |
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| 234 | |
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| 239 | |
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| 240 | <h3>Keywords</h3> |
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| 241 | |
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| 242 | <h4 id="_spl_keep_mean_keyword_YP0">YP0 |
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| 243 | |
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| 251 | </h4> |
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| 252 | |
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| 253 | <div class="comments"></div> |
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| 254 | |
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| 255 | <h4 id="_spl_keep_mean_keyword_YPN_1">YPN_1 |
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| 264 | </h4> |
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| 265 | |
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| 266 | <div class="comments"></div> |
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| 267 | |
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| 268 | <h4 id="_spl_keep_mean_keyword_GE0">GE0 |
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| 277 | </h4> |
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