title: Understanding loess errors in R
body: <p>I'm trying to fit a model using loess, and I'm getting errors such as "pseudoinverse used at 3", "neighborhood radius 1", and "reciprocal condition number  0".  Here's a MWE:</p>
  
  <pre><code>x = 1:19
  y = c(NA,71.5,53.1,53.9,55.9,54.9,60.5,NA,NA,NA
        ,NA,NA,178.0,180.9,180.9,NA,NA,192.5,194.7)
  fit = loess(formula = y ~ x,
          control = loess.control(surface = "direct"),
          span = 0.3, degree = 1)
  x2 = seq(0,20,.1)
  library(ggplot2)
  qplot(x=x2
      ,y=predict(fit, newdata=data.frame(x=x2))
      ,geom="line")
  </code></pre>
  
  <p>I realize I can fix these errors by choosing a larger span value.  However, I'm trying to automate this fit, as I have about 100,000 time series (each of length about 20) similar to this.  Is there a way that I can automatically choose a span value that will prevent these errors while still providing a fairly flexible fit to the data?  Or, can anyone explain what these errors mean?  I did a bit of poking around in the loess() and simpleLoess() functions, but I gave up at the point when C code was called.</p>