exercise5

library(datasets)
dat <- datasets::chickwts
list(dat)

## [[1]]
##    weight      feed
## 1     179 horsebean
## 2     160 horsebean
## 3     136 horsebean
## 4     227 horsebean
## 5     217 horsebean
## 6     168 horsebean
## 7     108 horsebean
## 8     124 horsebean
## 9     143 horsebean
## 10    140 horsebean
## 11    309   linseed
## 12    229   linseed
## 13    181   linseed
## 14    141   linseed
## 15    260   linseed
## 16    203   linseed
## 17    148   linseed
## 18    169   linseed
## 19    213   linseed
## 20    257   linseed
## 21    244   linseed
## 22    271   linseed
## 23    243   soybean
## 24    230   soybean
## 25    248   soybean
## 26    327   soybean
## 27    329   soybean
## 28    250   soybean
## 29    193   soybean
## 30    271   soybean
## 31    316   soybean
## 32    267   soybean
## 33    199   soybean
## 34    171   soybean
## 35    158   soybean
## 36    248   soybean
## 37    423 sunflower
## 38    340 sunflower
## 39    392 sunflower
## 40    339 sunflower
## 41    341 sunflower
## 42    226 sunflower
## 43    320 sunflower
## 44    295 sunflower
## 45    334 sunflower
## 46    322 sunflower
## 47    297 sunflower
## 48    318 sunflower
## 49    325  meatmeal
## 50    257  meatmeal
## 51    303  meatmeal
## 52    315  meatmeal
## 53    380  meatmeal
## 54    153  meatmeal
## 55    263  meatmeal
## 56    242  meatmeal
## 57    206  meatmeal
## 58    344  meatmeal
## 59    258  meatmeal
## 60    368    casein
## 61    390    casein
## 62    379    casein
## 63    260    casein
## 64    404    casein
## 65    318    casein
## 66    352    casein
## 67    359    casein
## 68    216    casein
## 69    222    casein
## 70    283    casein
## 71    332    casein

str(dat)

## 'data.frame':    71 obs. of  2 variables:
##  $ weight: num  179 160 136 227 217 168 108 124 143 140 ...
##  $ feed  : Factor w/ 6 levels "casein","horsebean",..: 2 2 2 2 2 2 2 2 2 2 ...

#we can see all feeds type by row
chickwts[,2]

##  [1] horsebean horsebean horsebean horsebean horsebean horsebean horsebean
##  [8] horsebean horsebean horsebean linseed   linseed   linseed   linseed  
## [15] linseed   linseed   linseed   linseed   linseed   linseed   linseed  
## [22] linseed   soybean   soybean   soybean   soybean   soybean   soybean  
## [29] soybean   soybean   soybean   soybean   soybean   soybean   soybean  
## [36] soybean   sunflower sunflower sunflower sunflower sunflower sunflower
## [43] sunflower sunflower sunflower sunflower sunflower sunflower meatmeal 
## [50] meatmeal  meatmeal  meatmeal  meatmeal  meatmeal  meatmeal  meatmeal 
## [57] meatmeal  meatmeal  meatmeal  casein    casein    casein    casein   
## [64] casein    casein    casein    casein    casein    casein    casein   
## [71] casein   
## Levels: casein horsebean linseed meatmeal soybean sunflower

#we can see all feeds type by column
chickwts["feed"] 

##         feed
## 1  horsebean
## 2  horsebean
## 3  horsebean
## 4  horsebean
## 5  horsebean
## 6  horsebean
## 7  horsebean
## 8  horsebean
## 9  horsebean
## 10 horsebean
## 11   linseed
## 12   linseed
## 13   linseed
## 14   linseed
## 15   linseed
## 16   linseed
## 17   linseed
## 18   linseed
## 19   linseed
## 20   linseed
## 21   linseed
## 22   linseed
## 23   soybean
## 24   soybean
## 25   soybean
## 26   soybean
## 27   soybean
## 28   soybean
## 29   soybean
## 30   soybean
## 31   soybean
## 32   soybean
## 33   soybean
## 34   soybean
## 35   soybean
## 36   soybean
## 37 sunflower
## 38 sunflower
## 39 sunflower
## 40 sunflower
## 41 sunflower
## 42 sunflower
## 43 sunflower
## 44 sunflower
## 45 sunflower
## 46 sunflower
## 47 sunflower
## 48 sunflower
## 49  meatmeal
## 50  meatmeal
## 51  meatmeal
## 52  meatmeal
## 53  meatmeal
## 54  meatmeal
## 55  meatmeal
## 56  meatmeal
## 57  meatmeal
## 58  meatmeal
## 59  meatmeal
## 60    casein
## 61    casein
## 62    casein
## 63    casein
## 64    casein
## 65    casein
## 66    casein
## 67    casein
## 68    casein
## 69    casein
## 70    casein
## 71    casein