Use asterisks to indicate level of statistical significance.
     
    
    
    Arguments
    - pvals
- numeric; vector of p-values. 
 
    
    Value
    
character vector of labels: p \(>\) 0.05 = "", 0.01 \(\leq\) p
\(<\) 0.05 = "*", 0.001 \(\leq\) p \(<\) 0.01 = "**", p \(<\) 0.001
  = "***"