<div dir="ltr"><div><div><div><div><div>Please look at the filtering examples:<br> <a href="https://www.ncl.ucar.edu/Applications/filter.shtml">https://www.ncl.ucar.edu/Applications/filter.shtml</a><br><br></div> In particular, run Example 8<br><br></div>[1] yes, of course ... more weights can create a sharper cutoff but there is a larger loass od data at the beginning and end.<br><br></div>[2] re: <span id="gmail-m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866">practical criterion .... That is up to you as a scientist.<br><br>--<br></span></div><span id="gmail-m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866">Note ncl-talk is not the place to learn about filtering.<br><br></span></div><span id="gmail-m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866">Good luck<br></span><div><div><span id="gmail-m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866"><br><br></span></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Dec 5, 2017 at 9:14 AM, Kiswendsida Hyacinthe GUIGMA <span dir="ltr"><<a href="mailto:karongseba@gmail.com" target="_blank">karongseba@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div style="color:#000;background-color:#fff;font-family:verdana,helvetica,sans-serif;font-size:16px"><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3785"><span id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3864">Dear NCL users,</span></div><div dir="ltr" id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3823"><span id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866">I am very new on NCL and I am trying to filter my rainfall data using Lanczos Filter (bandpass 10-90 day filtering). My question concerns the processing of the weights. I would like to know <br></span></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3884" dir="ltr"><span id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866">1-is there any relationship between the number of weights to choose and the cutoff frequencies?</span></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3929" dir="ltr"><span id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866">2-is there any practical criterion to choose the number of weights? I know that this number influences the loss of data.</span></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4139" dir="ltr"><span id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866">Below is my code:</span></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4147" dir="ltr"><span id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866"><br>------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>----------------</span></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3965" dir="ltr"><span id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3866">;import the file<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4027">gpcp=addfile("gpcp_Sahel.nc","<wbr>r")<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4028">rr=gpcp->precip<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4029">;filter parameters<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4030">ihp=2 ;bandpass<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4031">sigma=1.0 ; Lanczos sigma<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4032">nWgt = 81 ; number of weights -> means 40 data lost at the beginning and 40 data lost at the end. <br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4033">fca = 1./90. ; start freq ;highpass= 90 days<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4034">fcb = 1./10. ; last freq; lowpass= 10 days<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4035">wgt = filwgts_lanczos (nWgt, ihp, fca, fcb, sigma )<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4036">printVarSummary(wgt)<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4037">xBPF = wgt_runave_n_Wrap ( rr, wgt, 0, 0) ; 10-90 day bp performed across time dimension(0) of rr (meaning the time dimension)<br id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4038"></span></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3786"><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4166"> -----------------------------<wbr>------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>------------------------------<wbr>----------------</div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4167"><br></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4168"><br></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4157"><br></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4158"><br></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4169"><br></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_4170">Cheers,<br></div></div><div id="m_-6632467413770190592yui_3_16_0_ym19_1_1512489722799_3869" class="m_-6632467413770190592signature"><br>GUIGMA</div></div></div><br>______________________________<wbr>_________________<br>
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