title: Data summary with for loop
body: <p>I am trying to use the <code>summarySE</code> function from package <code>Rmisc</code> to generate data summaries for each column in a workbook. The first column in the worksheet is the grouping variable, and I want to loop through the other columns. 
  I am using the following code:</p>
  
  <pre><code>library(Rmisc)
  for(i in 2:ncol(file)){
      sum&lt;-summarySE(file, measurevar = file[,i], groupvars = file[1])
  }
  </code></pre>
  
  <p>But I keep getting the same error:</p>
  
  <pre><code>'Error in UseMethod("as.quoted") : 
   no applicable method for 'as.quoted' applied to an object of class    
   "data.frame"'
  </code></pre>
  
  <p>I know that <code>file[1]</code> is a <code>list</code> and should be a <code>vector</code>, but using <code>unlist</code> causes more problems. Any ideas?</p>
  
  <p>Data:</p>
  
  <pre><code>structure(list(Treatment = c("SKELE", "SKELE", "SKELE", "SKELE", 
  "SKELE", "SKELE", "SKELE", "SKELE", "SKELE", "SKELE", "SKELE", 
  "SKELE", "TISSUE", "TISSUE", "TISSUE", "TISSUE", "TISSUE", "TISSUE", 
  "TISSUE", "TISSUE", "TISSUE", "TISSUE", "TISSUE", "TISSUE"), 
  `% lipid in skeleton` = c(21.8706902567934, 31.1736436075643, 
  62.2246234617322, 86.6248675033794, 46.5607971373041, 34.7532319115317, 
  32.7686161366371, 6.73685660233744, 33.7111477556584, 48.8970450055359, 
  54.3687328279357, 48.9086732773318, 78.1293097432066, 68.8263563924357, 
  37.7753765382678, 13.3751324966206, 53.4392028626959, 65.2467680884683, 
  67.2313838633629, 93.2631433976626, 66.2888522443416, 51.1029549944641, 
  45.6312671720643, 51.0913267226682), `% ash in skeleton` = c(97.370981485225, 
  98.6169174273543, 99.2417548180554, 99.1330769035889, 98.5523872323069, 
  98.0077944962001, 97.7848485294277, 98.0738823145836, 98.1567971208113, 
  98.8047064451889, 97.1790753033603, 98.7503991978965, 2.62901851477497, 
  1.38308257264571, 0.75824518194458, 0.866923096411125, 1.44761276769314, 
  1.99220550379987, 2.2151514705723, 1.92611768541643, 1.84320287918869, 
  1.19529355481109, 2.82092469663973, 1.24960080210352), `% tissue in skeleton` = c(55.2224357342865, 
  70.022864703591, 77.5880978578982, 83.1168129092154, 67.3012504898307, 
  62.1455896726595, 64.2488985210074, 67.3089347382539, 59.9276126303114, 
  70.5681668501146, 67.717146912379, 68.8185249866557, 44.7775642657135, 
  29.977135296409, 22.4119021421018, 16.8831870907846, 32.6987495101694, 
  37.8544103273405, 35.7511014789926, 32.6910652617461, 40.0723873696886, 
  29.4318331498854, 32.2828530876211, 31.1814750133443)), class = "data.frame", row.names = c(NA, 
  -24L), .Names = c("Treatment", "% lipid in skeleton", "% ash in skeleton", 
  "% tissue in skeleton"))
  </code></pre>