title: Weighted linear regression in R
body: <p>I would like to do a linear regression with a weighting factor for an analytical chemistry calibration curve.  The x values are concentration and assumed to have no error.  The y values are instrument response and the variation is assumed proportional to concentration. So, I would like to use a 1/x weighting factor for the linear regression.  The data set is simply ten concentrations with a single measurement for each.  Is there an easy way to do this in R?  .</p>