title: Error: Coefficients: (4 not defined because of singularities) in R
body: <p>I have some error in my code, which I couldn't figure out.
  I have a dataframe "a", with:</p>
  
  <pre><code>row.names      GM      variance     stddev      skewness   correltomarket  DEratio
  1   MMM     0.9785122   0.9998918   0.9999459   -1.049053   2.932738    0.07252799
  </code></pre>
  
  <p>Now, I need to find a linear model for the above dataframe with the following code</p>
  
  <pre><code>riskmodel &lt;- lm(formula=((a$GM)~(a$variance)+(a$skewness)+
                           (a$correltomarket)+(a$DEratio)),data=a)
  </code></pre>
  
  <p>When I run this code, I get the following summary for the "riskmodel"</p>
  
  <pre><code>Call:
  lm(formula = ((a$GM) ~ (a$variance) + (a$skewness) + (a$correlationtomarket) + 
      (a$DEratio)), data = a)
  
  Residuals:
  ALL 1 residuals are 0: no residual degrees of freedom!
  
  Coefficients: (4 not defined because of singularities)
                        Estimate Std. Error t value Pr(&gt;|t|)
  (Intercept)             0.9785         NA      NA       NA
  a$variance                  NA         NA      NA       NA
  a$skewness                  NA         NA      NA       NA
  a$correlationtomarket       NA         NA      NA       NA
  a$DEratio                   NA         NA      NA       NA
  
  Residual standard error: NaN on 0 degrees of freedom
  </code></pre>
  
  <p>I don't understand why and I would be really grateful to anyone who helps me with this. I have no idea whats going wrong.</p>