title: filter rows that have X number of columns with value greater than Y
body: <p>I want to filter my data frame to keep only rows that have values > 5.5 in at least 2 columns. </p>
  
  <p>I know the <code>dplyr</code> function <code>filter(df,columnX&gt;5.5)</code>, but it only allows to take one or a few columns at a time. </p>
  
  <p>df:</p>
  
  <pre><code>    structure(list(tumor = c(5.69857588735462, 5.14269655336569, 
  15.5965461799242, 5.28949625542, 6.43237599127586, 5.21673785968077
  ), tumor = c(5.79729396999926, 5.10961482429376, 15.8339301491681, 
  5.47321124082556, 6.0624492087845, 5.21740033243091), tumor = c(5.67184459054712, 
  5.024088977993, 16.1659194908984, 5.20119456848026, 6.67441109230211, 
  5.15023836750153), tumor = c(5.9616857066853, 5.23907758025991, 
  15.2742729676712, 5.31827944648937, 6.47526325782951, 5.15926657492595
  ), tumor = c(5.75116456249489, 5.03195808382708, 16.0180448251626, 
  5.36575242301428, 6.85603803194346, 5.18022831262029)), class = "data.frame", row.names = c("A_33_P3390097", 
  "NM_178466", "GE_BrightCorner", "ENST00000396843", "NM_001166137", 
  "DarkCorner"))
  </code></pre>