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    <div class="moz-cite-prefix">I appreciate your help; however,
      neither suggestion works: I still get the same error message.<br>
      The similar line <br>
              [frq,repf]=repfreq(hz,0.01,0.49);<br>
      has no problem<br>
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    <blockquote cite="mid:56CC6DE0.7040602@inria.fr" type="cite">
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      <div class="moz-cite-prefix">Your problem arises because one
        frequency value you ask for  corresponds exactly to a zero of
        hz.num<br>
        log(roots(hz.num))/(2*%pi)<br>
        so you want to compute the gain in dB of a zero value which is
        -inf<br>
        <br>
        To avoid such problem you can let repfreq to do the frequency
        discretization.<br>
        <pre class="scilabcode"><span class="scilabopenclose"><span class="scilabopenclose">[</span><span class="scilabid">frq</span><span class="scilabdefault">,</span><span class="scilabid">repf</span><span class="scilabopenclose">]</span><span class="scilaboperator">=</span><a moz-do-not-send="true" class="scilabmacro" href="repfreq.html">repfreq</a><span class="scilabopenclose">(</span><span class="scilabid">hz</span><span class="scilabdefault">)</span>
or equivalently
[</span><span class="scilabid">frq</span><span class="scilabdefault">,</span><span class="scilabid">repf</span><span class="scilabopenclose">]</span><span class="scilaboperator">=</span><a moz-do-not-send="true" class="scilabmacro" href="repfreq.html">repfreq</a><span class="scilabopenclose">(</span><span class="scilabid">hz</span><span class="scilabdefault">,0,0.5)</span></pre>
        in  this case the discretization uses  varying  frequency step<br>
        Serge<br>
        <br>
        Le 23/02/2016 14:41, grivet a écrit :<br>
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      <blockquote cite="mid:56CC617F.3000508@cnrs-orleans.fr"
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        <div class="moz-cite-prefix">Le 23/02/2016 14:21, Serge Steer a
          écrit :<br>
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        <blockquote cite="mid:56CC5CC1.1050607@inria.fr" type="cite">
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          <div class="moz-cite-prefix">Please can you give more details
            :<br>
            value of Order and Fcutoff/Fs/2<br>
            and what you are doing with hz (because iir does not call
            dbphi)<br>
            Serge<br>
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