*****Brain Weight Data, SW text ex 2.12 pp. 22-23******** Stat141 9/26/06
> brain = read.table(file="D:\\stat141\\brain-wt.rData", header = T)
> summary(brain)
    brainwt     sex    
 Min.   : 915   f: 77  
 1st Qu.:1096   m:108  
 Median :1211          
 Mean   :1207          
 3rd Qu.:1300          
 Max.   :1660

> stem(brain$brainwt)
  The decimal point is 2 digit(s) to the right of the |
   9 | 24
   9 | 56788
  10 | 001122233334444444
  10 | 555556677799999999
  11 | 00000111111222233334444
  11 | 555667777788888899999
  12 | 000011122233333333333334444
  12 | 555555555666667777788899
  13 | 0000111111222334444
  13 | 555666788999
  14 | 0111224
  14 | 68
  15 | 134
  15 | 56
  16 | 1
  16 | 6
#histograms text p.23

percvec = seq(0,1,.1) #make percentile values for min to max           
> quantile(brain$brainwt, percvec)
    0%    10%    20%    30%    40%    50%    60%    70%    80%    90%   100% 
 915.0 1035.8 1085.0 1117.6 1170.0 1211.0 1235.8 1269.0 1311.0 1383.0 1660.0

         #condition on sex
> tapply(brain$brainwt, brain$sex, summary)
$f Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
    937    1038    1096    1117    1190    1392 
$m Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
    915    1193    1260    1271    1344    1660 

> tapply(brain$brainwt, brain$sex, stem)
  The decimal point is 2 digit(s) to the right of the |
#female                                 #male
   9 | 4                                9 | 2                  
   9 | 56788                            9 |                    
  10 | 0011223334444444                10 | 23                 
  10 | 5555667799999                   10 | 57999              
  11 | 00001112233344                  11 | 011122344          
  11 | 557788889                       11 | 566777889999       
  12 | 000123334                       12 | 011223333333333444 
  12 | 5555678                         12 | 55555666677778899  
  13 | 24                              13 | 00001111112233444  
  13 | 9                               13 | 55566678899        
                                       14 | 0111224            
                                       14 | 68                 
                                       15 | 134                
                                       15 | 56                 
                                       16 | 1                  
                                       16 | 6