title: How to do a weighted fit for a with a set of data containing f(x) +- df(x)?
body: <p>I have a function <code>f(x) = a/x</code> and I have a set of data containing values for <code>f(x) +- df(x)</code> and <code>x +- dx</code>. How do I tell gnuplot to do a weighted fit for <code>a</code> with that?</p>
  
  <p>I know that <code>fit</code>accepts the <code>using</code> term and this works for <code>df(x)</code>, but it does not work for <code>dx</code>. It seems gnuplot treats the error I have for <code>x</code> as the error for the whole RHS of my function (<code>a/x +- dx</code>).</p>
  
  <p>How do I do a weighted fit that fits <code>f(x) +- df(x) = a/(x +- dx)</code> to find the optimal <code>a</code>?</p>