# Quiz answers


# rows 1:10 of the first two columns 

         1:10  1:2
    sup3[c(1,2,3,4,5,6,7,8,9,10), c(1,2)]
    sup3[1:10, 1:2]








# rows 1:10 of the first two columns in reverse order

         10:1
    sup3[10:1, 1:2]









# rows 1:10 of the first two columns in reverse order,
# but not the third row of the result

     sup3[10:1, 1:2]
    (sup3[10:1, 1:2])[-3, ]









# rows 1:10 of the first two columns in random order
#     hint: use sample()

         sample(1:10)
    sup3[sample(1:10), 1:2]









# rows 1:10 of the first two columns, ordered by
# the value in the second column, ascending
#     hint: use order()

           sup3[1:10,2]
     order(sup3[1:10,2])
sup3[order(sup3[1:10,2]), 1:2]









# rows 1:10 of the column named Mo.LPS

    sup3[1:10, "Mo.LPS"]
    sup3$Mo.LPS[1:10]
    
    
    
    
    
    
    
    

# rows 1:10 of the columns named Mo.LPS and Mo.ctrl

    sup3[1:10, c("Mo.LPS", "Mo.ctrl")]
    
    
    
    
    
    
    
    



# all genes with gene-names that are three characters long

               sup3$genes
         nchar(sup3$genes)
         nchar(sup3$genes) == 3
    sup3$genes[nchar(sup3$genes) == 3]
    
    
    
    
    
    
    
    


# column 1:2 of all rows with gene-names that contain
# the string "Il"

         grep("Il", "IlInThisString")
         grep("Il", "NoneInThisString")   # not 
         grep("Il", sup3$genes)
    sup3[grep("Il", sup3$genes), 1:2]








# all genes for which B-cells are stimulated by LPS by
# more than 2 log units.

          sup3$B.ctrl - sup3$B.LPS
         (sup3$B.ctrl - sup3$B.LPS) < -2
    sup3[(sup3$B.ctrl - sup3$B.LPS) < -2, 1:3]






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