title: How do I make a loop to extract a column from multiple lists and then bind them together to make a new matrix?
body: <p>I am new to looping and R in general; and I have sent waaaay to much time on this one problem and am about a hair away from doing it manually for the next two days.</p>
  
  <p>So, there is a package that while calculating the statistic creates lists (that look like matrices) in the background.  Each item (there are 10 items) has one of these ‘matrix looking list’ that I need to extract data from. The list has 5 rows that represent 5 groups, and 8 columns.  I need to extract 3 of the columns (‘Lo Score’=[,2], ‘Hi Score=[,3]’, and ‘Mean’=[,7]) for each of the items.  I then want to turn the extracted data into 3 matrices (‘Lo Score’, ‘Hi Score’, and ‘Mean’) where the rows are the 5 groups and the columns are items 1-10.</p>
  
  <p>This is how I can create the mean matrix by hand.  “MDD.mean.s10” is the matrix I want in the end.  (notice the first bracket after $results is the only part that changes 1-10 (to represent the 10 items) and the last bracket is [,7] to represent the mean located in column 7)</p>
  
  <pre><code>m.1a &lt;- MC_MDD.noNA$results[[1]][[2]][,7]
  m.2b &lt;- MC_MDD.noNA$results[[2]][[2]][,7]
  m.3c &lt;- MC_MDD.noNA$results[[3]][[2]][,7]
  m.4d &lt;- MC_MDD.noNA$results[[4]][[2]][,7]
  m.5e &lt;- MC_MDD.noNA$results[[5]][[2]][,7]
  m.6f &lt;- MC_MDD.noNA$results[[6]][[2]][,7]
  m.7g &lt;- MC_MDD.noNA$results[[7]][[2]][,7]
  m.8h &lt;- MC_MDD.noNA$results[[8]][[2]][,7]
  m.9i &lt;- MC_MDD.noNA$results[[9]][[2]][,7]
  m.10j &lt;- MC_MDD.noNA$results[[10]][[2]][,7]
  MDD.mean.s10 &lt;- cbind(m.1a, m.2b, m.3c, m.4d, m.5e, m.6f, m.7g, m.8h, m.9i, m.10j)
  
  MDD.mean.s10   
  
           m.1a      m.2b      m.3c      m.4d      m.5e      m.6f      m.7g      m.8h      m.9i     m.10j
  [1,] 0.8707865 0.7393939 0.7769231 0.7591241 0.8533333 0.7925926 0.8258065 0.8410596 0.8843931 0.5638298
  [2,] 0.8323353 0.7302632 0.5913978 0.5868263 0.6923077 0.6182796 0.6964286 0.6839080 0.7911392 0.3212121
  [3,] 0.8726115 0.7159763 0.7117647 0.6163522 0.7987805 0.7105263 0.7613636 0.7674419 0.8034682 0.4011299
  [4,] 0.9024390 0.7894737 0.7795276 0.6530612 0.8593750 0.7112676 0.8672566 0.8629032 0.9152542 0.4834437
  [5,] 0.9861111 0.9102564 0.8452381 0.8160920 0.9726027 0.8658537 0.8352941 0.9342105 0.9466667 0.6454545
  </code></pre>
  
  <p>But I can’t do this by hand every time, as this comes up over and over and over again in multiple lists.
  I have figured out how to loop this procedure and name the vector as it goes along:</p>
  
  <pre><code>for(i in 1:10){
  assign(paste("m", i, sep = ""), MC_MDD.noNA$results[[i]][[2]][,7])
  }
  
  m1
  [1] 0.8707865 0.8323353 0.8726115 0.9024390 0.9861111
  m2
  0.7393939 0.7302632 0.7159763 0.7894737 0.9102564
  m3
  [1] 0.7769231 0.5913978 0.7117647 0.7795276 0.8452381
  m4
  [1] 0.7591241 0.5868263 0.6163522 0.6530612 0.8160920
  m5
  [1] 0.8533333 0.6923077 0.7987805 0.8593750 0.9726027
  m6
  [1] 0.7925926 0.6182796 0.7105263 0.7112676 0.8658537
  m7
  [1] 0.8258065 0.6964286 0.7613636 0.8672566 0.8352941
  m8
  [1] 0.8410596 0.6839080 0.7674419 0.8629032 0.9342105
  m9
  [1] 0.8843931 0.7911392 0.8034682 0.9152542 0.9466667
  m10
  [1] 0.5638298 0.3212121 0.4011299 0.4834437 0.6454545
  </code></pre>
  
  <p>Now here where I get stuck… how do I cbind these vectors without typing it out expliciity? ie. mean.MDD &lt;- cbind(m1,m2,m3,m4,m5,m6,m7,m8,m9,10)</p>
  
  <p>Everything I have tried keeps overwriting the data instead of building a matrix.  Basically I, start with a matrix (5x10) of zeros.  Then I wind up with a few values in the beginning, but the rest is still zeros.
  Examples of terrible code:</p>
  
  <pre><code>fo &lt;- matrix(0,5,10)
  colnames(fo) &lt;- paste('f', 1:10, sep = "")
  fo
        f1 f2 f3 f4 f5 f6 f7 f8 f9 f10
  [1,]  0  0  0  0  0  0  0  0  0   0
  [2,]  0  0  0  0  0  0  0  0  0   0
  [3,]  0  0  0  0  0  0  0  0  0   0
  [4,]  0  0  0  0  0  0  0  0  0   0
  [5,]  0  0  0  0  0  0  0  0  0   0
  for(i in 1:10){
  fo &lt;- assign(paste("f", i, sep = ""), MC_MDD.noNA$results[[i]][[2]][,7])
  }
  fo
  [1] 0.5638298 0.3212121 0.4011299 0.4834437 0.6454545
  
  fo &lt;- matrix(0,5,10)
  colnames(fo) &lt;- paste('f', 1:10, sep = "")
  fo
        f1 f2 f3 f4 f5 f6 f7 f8 f9 f10
  [1,]  0  0  0  0  0  0  0  0  0   0
  [2,]  0  0  0  0  0  0  0  0  0   0
  [3,]  0  0  0  0  0  0  0  0  0   0
  [4,]  0  0  0  0  0  0  0  0  0   0
  [5,]  0  0  0  0  0  0  0  0  0   0
  for(i in 1:10){
  fo &lt;- cbind(assign(paste("f", i, sep = ""), MC_MDD.noNA$results[[i]][[2]][,7]))
  }
  fo
  [,1]
  [1,] 0.5638298
  [2,] 0.3212121
  [3,] 0.4011299
  [4,] 0.4834437
  [5,] 0.6454545
  </code></pre>
  
  <p>Thanks for your help in advance!!!  (c:</p>