title: adf test and acf plot on multiple columns
body: <p>I am trying to apply adf.test to all columns of a dataframe. Some columns have NA values. I would like to store the output in a vector/list/dataframe.</p>
  
  <pre><code>H&lt;-data.frame(replicate(10,sample(0:20,10,rep=TRUE))) 
  H[c(2,3,7,9),9]&lt;-NA
  H[c(1,4,8),2]&lt;-NA
  H[c(1,2,3,4,8),4]&lt;-NA
  </code></pre>
  
  <p>I get errors as below</p>
  
  <pre><code>oi&lt;-adf.test(H,alternative="stationary")
  Error in adf.test(H, alternative = "stationary") : 
    x is not a vector or univariate time series
  
  lapply(na.omit(H),adf.test)
  Error in res.sum$coefficients[2, 1] : subscript out of bounds
  </code></pre>
  
  <p>Package: tseries</p>
  
  <p>Help is appreciated</p>