title: Identify outliers in scatter plot
body: <p>I have a dataset that looks like this:</p>
  
  <pre><code>gene        AE        CM       PR     CD34     
  DDR1  8.020745  7.851901 7.520458 7.948326  
  RFC2  7.778460  8.175659 7.978560 8.845708 
  PAX8  9.566903  9.589379 9.405003 8.853069  
  GUCA1A  5.320824  5.318613 5.333363 5.424622 
  UBA7 10.422949 10.193109 9.357451 9.985480 
  GAPDH 13.559894 13.739593 13.517791 12.047161 
  GAPD 13.619479 13.790955 13.670576 12.994784 
  STAT_1 10.175952  9.911392  9.424882 10.024869  
  STAT3  7.089633  6.898931  6.654907  5.894336  
  STAT4  8.843160  8.746647  8.389753  8.024894 
  </code></pre>
  
  <p>I wanted to have a scatterplot for each of the possible pairs and for that I used following R commands</p>
  
  <pre><code>d&lt;-read.table("Dataset.txt", header=T, sep="\t")
  pairs(~d$AE+d$CM+d$PR+d$CD34,col="red")
  </code></pre>
  
  <p>Now what more, I want is to have the outliers marked with the gene names. for instance, DDR1 has a difference of 0.5 between AE Vs CD34. Hence this should be marked in that plot with gene name (in this case DDR1).</p>
  
  <p>Overall, any gene between the pairs showing a difference of +- 0.5 should be marked.</p>
  
  <p><strong>Data:</strong> The result of <code>dput()</code> of first 100 lines of my data</p>
  
  <pre><code>    structure(list(gene = structure(c(25L, 57L, 38L, 47L, 36L), .Label = c("ADAM32", 
  "AFG3L1", "AKD1", "ALG10", "ARMCX4", "ATP6V1E2", "BEST4", "C15orf40", 
  "C19orf26", "C4orf33", "C8orf45", "C8orf47", "C9orf30", "CATSPER1", 
  "CCDC11", "CCDC65", "CCL5", "CILP2", "CNOT7", "CORO6", "CRYZL1", 
  "CTCFL", "CYP2A6", "CYP2E1", "DDR1", "EPHB3", "ESRRA", "EYA3", 
  "FAM122C", "FAM18B2", "FAM71A", "FLJ30901", "GAPT", "GIMAP1", 
  "GSC", "GUCA1A", "HOXD4", "HSPA6", "KLK8", "LEAP2", "MAPK1", 
  "MFAP3", "MGC16385", "MSI2", "NCRNA00152", "NEXN", "PAX8", "PDE7A", 
  "PIGX", "PRR22", "PRSS33", "PTPN21", "PXK", "RAX2", "RBBP6", 
  "RDH10", "RFC2", "SCARB1", "SCIN", "SLC39A13", "SLC39A5", "SLC46A1", 
  "SP7", "SPATA17", "SRrp35", "THRA", "TIMD4", "TIRAP", "TMEM106A", 
  "TMEM196", "TRIOBP", "TTC39C", "TTLL12", "UBA7", "VPS18", "WFDC2", 
  "ZDHHC11", "ZNF333"), class = "factor"), AE = c(8.0207450402, 
  7.7784602732, 7.274639204, 9.5669027802, 5.3208241196), CM = c(7.8519007358, 
  8.1756591822, 7.8186806878, 9.5893790363, 5.3186130064), PR = c(7.5204580759, 
  7.9785595029, 7.3307638794, 9.4050027059, 5.3333625256), CD34 = c(7.9483258833, 
  8.8457084131, 6.9874872331, 8.8530693617, 5.4246223945), CMP = c(7.9362235824, 
  10.0085488406, 6.6883401632, 9.249816924, 5.4312885508), GMP = c(8.1370096058, 
  10.0990080444, 6.7144163183, 9.2157346882, 5.3700062534), Monocytes = c(8.1912723165, 
  8.7568163628, 9.2072172453, 9.2086040758, 5.3090689608)), .Names = c("gene", 
  "AE", "CM", "PR", "CD34", "CMP", "GMP", "Monocytes"), row.names = c(NA, 
  5L), class = "data.frame")
  </code></pre>