Thanks Oswin, <br>I think this should be included in the documentation, (See <a href="http://stackoverflow.com/q/7501996/894755">here</a>). Beginners like me can&#39;t find this easily.<br>I didn&#39;t understand your note about const_iterator. <br>

<br>Regards,<br>Tarek<br><br>On Wed, Sep 21, 2011 at 6:47 PM, Oswin Krause &lt;<a href="mailto:Oswin.Krause@ruhr-uni-bochum.de">Oswin.Krause@ruhr-uni-bochum.de</a>&gt; wrote:<br>&gt;&gt; Hello,<br>&gt;&gt; How can I know the index of the first non-zero element in a<br>

&gt;&gt; sparse_vector in ublas and each subsequent nonzero element as well?<br>&gt;&gt; The function begin() gives me an iterator that can be used to know the<br>&gt;&gt; first non-zero value stored, not its index in the vector.<br>

&gt;&gt; Tarek<br>&gt; Iterators offer a method index() which returns the desired result. But<br>&gt; remember that only the const_iterator is really sparse!<br>&gt;<br>&gt; for(SparseVector::const_iterator pos = sparseVec.begin(); pos !=<br>

&gt; sparseVec.end();++pos){<br>&gt; std::cout &lt;&lt; pos.index()&lt;&lt; &quot; &quot;&lt;&lt; *pos;<br>&gt; }<br>&gt;<br>&gt; Greetings,<br>&gt; Oswin<br>&gt;<br>&gt; _______________________________________________<br>

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