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POMatching two grids for data analysis, is there a good algorithm for my problem?
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  1. POMatching two grids for data analysis, is there a good algorithm for my problem?
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    copied!<p>I'd like to compare two differently spaced datasets in python. I always want to find the closest (nearest neighbour) match and regrid the data, see this example:</p> <p>Dataset A:</p> <pre><code>ALTITUDE[m] VALUE 1. a1 2. a2 3. a3 4. a4 </code></pre> <p>Dataset B:</p> <pre><code>ALTITUDE[m] VALUE 0.7 b1 0.9 b2 1.7 b3 2. b4 2.4 b5 2.9 b6 3.1 b7 3.2 b8 3.9 b9 4.1 b10 </code></pre> <p><code>ai</code> and <code>bi</code> contain double numbers, but also <code>nan</code> fields.</p> <p>I'd like to transform dataset B to the altitude grid of dataset A, but since dataset A contains less altitude levels than dataset B, I'd like to average them.</p> <pre><code>ALTITUDE[m] VALUE 1. median(b1,b2) 2. median(b3,b4,b5) 3. median(b6,b7,b8) 4. median(b9,b10) </code></pre> <p>i.e. the closest altitude levels have been found and averaged over. </p> <p>Conversely, if I want to match dataset A to the grid of dataset B, dataset A should look like this (nearest neighbour):</p> <pre><code>ALTITUDE[m] VALUE 0.7 a1 0.9 a1 1.7 a2 2. a2 2.4 a2 2.9 a3 3.1 a3 3.2 a3 3.9 a4 4.1 a4 </code></pre> <p>Maybe this even has a name (I imagine it being a common problem), but I don't know it and thus cannot search for it. I believe there is an efficient way of doing this, apart from the obvious solution coding it myself (but I'm afraid it won't be efficient and I'd introduce many bugs).</p> <p>Preferably using numpy.</p> <p><strong>EDIT:</strong> Thanks for your input to all four contributors. I learned a bit and I apologize for not asking very clearly. I was myself in the progress of understanding the problem. Your answers pointed me towards the usage of <code>interp1d</code> and this <a href="https://stackoverflow.com/questions/2745329/how-to-make-scipy-interpolate-give-a-an-extrapolated-result-beyond-the-input-rang/2745496#2745496">answer</a> allowed me to abuse it for me. I will post the result shortly. I can accept only one answer, but anyone would do.</p>
 

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