#Nedostajuci podaci
##Missing values rijesavamo na na slijedeci nacin:

#uzmimo opet bazu WHO

WHO <- read.csv("WHO.csv") #navodnici su veoma bitni ovdje!
table(is.na(WHO)) #pokazuje nam koliko imamo polja u bazi podataka koji su NA
## 
## FALSE  TRUE 
##  2192   330
#drug nacin da vidimo koliko svaka varjabla ima je

summary(WHO)
##    Country             Region            Population         Under15     
##  Length:194         Length:194         Min.   :      1   Min.   :13.12  
##  Class :character   Class :character   1st Qu.:   1696   1st Qu.:18.72  
##  Mode  :character   Mode  :character   Median :   7790   Median :28.65  
##                                        Mean   :  36360   Mean   :28.73  
##                                        3rd Qu.:  24535   3rd Qu.:37.75  
##                                        Max.   :1390000   Max.   :49.99  
##                                                                         
##      Over60      FertilityRate   LifeExpectancy  ChildMortality   
##  Min.   : 0.81   Min.   :1.260   Min.   :47.00   Min.   :  2.200  
##  1st Qu.: 5.20   1st Qu.:1.835   1st Qu.:64.00   1st Qu.:  8.425  
##  Median : 8.53   Median :2.400   Median :72.50   Median : 18.600  
##  Mean   :11.16   Mean   :2.941   Mean   :70.01   Mean   : 36.149  
##  3rd Qu.:16.69   3rd Qu.:3.905   3rd Qu.:76.00   3rd Qu.: 55.975  
##  Max.   :31.92   Max.   :7.580   Max.   :83.00   Max.   :181.600  
##                  NA's   :11                                       
##  CellularSubscribers  LiteracyRate        GNI       
##  Min.   :  2.57      Min.   :31.10   Min.   :  340  
##  1st Qu.: 63.57      1st Qu.:71.60   1st Qu.: 2335  
##  Median : 97.75      Median :91.80   Median : 7870  
##  Mean   : 93.64      Mean   :83.71   Mean   :13321  
##  3rd Qu.:120.81      3rd Qu.:97.85   3rd Qu.:17558  
##  Max.   :196.41      Max.   :99.80   Max.   :86440  
##  NA's   :10          NA's   :91      NA's   :32     
##  PrimarySchoolEnrollmentMale PrimarySchoolEnrollmentFemale
##  Min.   : 37.20              Min.   : 32.50               
##  1st Qu.: 87.70              1st Qu.: 87.30               
##  Median : 94.70              Median : 95.10               
##  Mean   : 90.85              Mean   : 89.63               
##  3rd Qu.: 98.10              3rd Qu.: 97.90               
##  Max.   :100.00              Max.   :100.00               
##  NA's   :93                  NA's   :93
##zasto moramo "znati" kako rukovati sa Na?----
#imamo nekih funkcija koje ne mozemo raditi i R nam prikazuje NA kao rezultat ili nekada kao gresku. npr mean tj. srednja vrijednost

mean(WHO$LiteracyRate)
## [1] NA
mean(WHO$LiteracyRate, na.rm = T) #na ovaj nacin eliminisemo Na iz racunice tj. u srednjoj vrijednosti zemlje koje nemaju podatak o stopi pismenosti nisu usle u racunicu
## [1] 83.71068
##Ako zelimo u potpunosti da iz cijele baze izbacimo sve obzervacije koje po bilo kojoj varijabli imaju NA onda: 

WHObezNA <- na.omit (WHO) #Na ovaj nacin formirali smo novu bazu bezNA koja ne sadrzi NA.
WHObezNA
##                                       Country                Region Population
## 5                                      Angola                Africa      20821
## 6                         Antigua and Barbuda              Americas         89
## 22                     Bosnia and Herzegovina                Europe       3834
## 32                                 Cape Verde                Africa        494
## 33                   Central African Republic                Africa       4525
## 37                                   Colombia              Americas      47704
## 43                                    Croatia                Europe       4307
## 52                         Dominican Republic              Americas      10277
## 55                                El Salvador              Americas       6297
## 56                          Equatorial Guinea                Africa        736
## 57                                    Eritrea                Africa       6131
## 58                                    Estonia                Europe       1291
## 64                                     Gambia                Africa       1791
## 68                                     Greece                Europe      11125
## 70                                  Guatemala              Americas      15083
## 71                                     Guinea                Africa      11451
## 72                              Guinea-Bissau                Africa       1664
## 75                                   Honduras              Americas       7936
## 76                                    Hungary                Europe       9976
## 84                                      Italy                Europe      60885
## 87                                     Jordan Eastern Mediterranean       7009
## 94                                     Latvia                Europe       2060
## 96                                    Lesotho                Africa       2052
## 99                                  Lithuania                Europe       3028
## 105                                      Mali                Africa      14854
## 108                                Mauritania                Africa       3796
## 110                                    Mexico              Americas     121000
## 113                                  Mongolia       Western Pacific       2796
## 116                                Mozambique                Africa      25203
## 118                                   Namibia                Africa       2259
## 125                                   Nigeria                Africa     169000
## 131                                    Panama              Americas       3802
## 133                                  Paraguay              Americas       6687
## 136                                    Poland                Europe      38211
## 137                                  Portugal                Europe      10604
## 138                                     Qatar Eastern Mediterranean       2051
## 140                       Republic of Moldova                Europe       3514
## 141                                   Romania                Europe      21755
## 150                              Saudi Arabia Eastern Mediterranean      28288
## 152                                    Serbia                Europe       9553
## 157                                  Slovenia                Europe       2068
## 162                                     Spain                Europe      46755
## 163                                 Sri Lanka       South-East Asia      21098
## 170                                Tajikistan                Europe       8009
## 172 The former Yugoslav Republic of Macedonia                Europe       2106
## 181                                    Uganda                Africa      36346
## 182                                   Ukraine                Europe      45530
## 188                                Uzbekistan                Europe      28541
## 192                                     Yemen Eastern Mediterranean      23852
## 193                                    Zambia                Africa      14075
##     Under15 Over60 FertilityRate LifeExpectancy ChildMortality
## 5     47.58   3.84          6.10             51          163.5
## 6     25.96  12.35          2.12             75            9.9
## 22    16.35  20.52          1.26             76            6.7
## 32    30.17   7.05          2.38             72           22.2
## 33    40.07   5.74          4.54             48          128.6
## 37    28.03   9.19          2.35             78           17.6
## 43    14.98  24.69          1.48             77            4.7
## 52    30.53   8.97          2.55             73           27.1
## 55    30.62   9.64          2.24             72           15.9
## 56    38.95   4.53          5.04             54          100.3
## 57    43.10   3.73          4.88             61           51.8
## 58    15.69  23.92          1.62             76            3.6
## 64    45.90   3.72          5.79             58           72.9
## 68    14.60  25.41          1.51             81            4.8
## 70    40.80   6.56          3.91             69           32.0
## 71    42.46   5.03          5.09             55          101.2
## 72    41.55   5.06          5.05             50          129.1
## 75    35.72   6.41          3.10             74           22.9
## 76    14.62  23.41          1.38             75            6.2
## 84    14.04  26.97          1.45             82            3.8
## 87    34.13   5.30          3.39             74           19.1
## 94    14.57  24.24          1.57             74            8.7
## 96    36.75   6.31          3.15             50           99.6
## 99    15.13  20.57          1.49             74            5.4
## 105   47.14   4.29          6.85             51          128.0
## 108   40.22   4.94          4.78             59           84.0
## 110   29.02   9.18          2.25             75           16.2
## 113   27.05   5.80          2.45             68           27.5
## 116   45.38   5.01          5.34             53           89.7
## 118   36.59   5.38          3.17             65           38.7
## 125   44.23   4.49          6.02             53          123.7
## 131   28.65  10.13          2.52             77           18.5
## 133   32.78   8.01          2.93             75           22.0
## 136   14.91  20.48          1.39             76            5.0
## 137   14.92  24.39          1.33             80            3.6
## 138   13.28   1.73          2.06             82            7.4
## 140   16.52  16.72          1.47             71           17.6
## 141   15.05  20.66          1.39             74           12.2
## 150   29.69   4.59          2.76             76            8.6
## 152   16.45  20.52          1.37             74            6.6
## 157   14.16  23.16          1.49             80            3.1
## 162   15.20  22.86          1.47             82            4.5
## 163   25.15  12.40          2.35             75            9.6
## 170   35.75   4.80          3.81             68           58.3
## 172   16.89  17.56          1.44             75            7.4
## 181   48.54   3.72          6.06             56           68.9
## 182   14.18  20.76          1.45             71           10.7
## 188   28.90   6.38          2.38             68           39.6
## 192   40.72   4.54          4.35             64           60.0
## 193   46.73   3.95          5.77             55           88.5
##     CellularSubscribers LiteracyRate   GNI PrimarySchoolEnrollmentMale
## 5                 48.38         70.1  5230                        93.1
## 6                196.41         99.0 17900                        91.1
## 22                84.52         97.9  9190                        86.5
## 32                79.19         84.3  3980                        94.6
## 33                40.65         56.0   810                        81.3
## 37                98.45         93.4  9560                        91.7
## 43               116.37         98.8 18760                        94.8
## 52                87.22         89.5  9420                        95.5
## 55               133.54         84.5  6640                        95.2
## 56                59.15         93.9 25620                        56.5
## 57                 4.47         67.8   580                        37.2
## 58               138.98         99.8 20850                        97.7
## 64                78.89         50.0  1750                        68.2
## 68               106.48         97.2 25100                        98.8
## 70               140.38         75.2  4760                        98.6
## 71                44.02         41.0  1020                        85.2
## 72                56.18         54.2  1240                        76.7
## 75               103.97         84.8  3820                        94.8
## 76               117.30         99.0 20310                        97.8
## 84               157.93         98.9 32400                        99.6
## 87               118.20         92.6  5930                        90.8
## 94               102.94         99.8 17700                        95.0
## 96                56.17         89.6  2050                        72.2
## 99               151.30         99.7 19640                        95.6
## 105               68.32         31.1  1040                        70.6
## 108               93.60         58.0  2400                        72.8
## 110               82.38         93.1 15390                        99.2
## 113              105.08         97.4  4290                        99.6
## 116               32.83         56.1   970                        94.6
## 118               96.39         88.8  6560                        83.8
## 125               58.58         61.3  2290                        60.1
## 131              188.60         94.1 14510                        99.1
## 133               99.40         93.9  5390                        84.4
## 136              130.97         99.5 20430                        96.9
## 137              115.39         95.2 24440                        99.1
## 138              123.11         96.3 86440                        95.7
## 140              104.80         98.5  3640                        90.1
## 141              109.16         97.7 15120                        87.9
## 150              191.24         86.6 24700                        96.7
## 152              125.39         97.9 11540                        94.7
## 157              106.56         99.7 26510                        97.7
## 162              113.22         97.7 31400                        99.7
## 163               87.05         91.2  5520                        93.9
## 170               90.64         99.7  2300                        99.5
## 172              107.24         97.3 11090                        97.3
## 181               48.38         73.2  1310                        89.7
## 182              122.98         99.7  7040                        90.8
## 188               91.65         99.4  3420                        93.3
## 192               47.05         63.9  2170                        85.5
## 193               60.59         71.2  1490                        91.4
##     PrimarySchoolEnrollmentFemale
## 5                            78.2
## 6                            84.5
## 22                           88.4
## 32                           92.4
## 33                           60.6
## 37                           91.3
## 43                           97.0
## 52                           90.4
## 55                           95.5
## 56                           56.0
## 57                           32.5
## 58                           97.0
## 64                           70.4
## 68                           99.3
## 70                           97.5
## 71                           72.1
## 72                           73.3
## 75                           97.0
## 76                           98.3
## 84                           98.5
## 87                           90.7
## 94                           96.8
## 96                           75.3
## 99                           95.8
## 105                          60.8
## 108                          76.0
## 110                          99.9
## 113                          98.5
## 116                          89.4
## 118                          88.5
## 125                          54.8
## 131                          98.2
## 133                          83.9
## 136                          96.7
## 137                          99.7
## 138                          96.6
## 140                          90.1
## 141                          87.3
## 150                          96.5
## 152                          94.4
## 157                          97.3
## 162                          99.8
## 163                          94.4
## 170                          96.0
## 172                          99.2
## 181                          92.3
## 182                          91.5
## 188                          91.0
## 192                          70.5
## 193                          93.9
table (is.na(WHObezNA)) #dakle nemamo NA
## 
## FALSE 
##   650
#izuzece NA iz odredjene varijable

table(is.na(WHO$PrimarySchoolEnrollmentFemale))#prvo provjerimo koliko imamo Na
## 
## FALSE  TRUE 
##   101    93
summary(WHO$PrimarySchoolEnrollmentFemale)
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max.    NA's 
##   32.50   87.30   95.10   89.63   97.90  100.00      93
WHOPSEFnona <- WHO[complete.cases(WHO$PrimarySchoolEnrollmentFemale),] #ovo je ispravniji nacin od na.omit ()

summary (WHOPSEFnona$PrimarySchoolEnrollmentFemale)
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##   32.50   87.30   95.10   89.63   97.90  100.00
table(is.na(WHOPSEFnona$PrimarySchoolEnrollmentFemale)) #vidimo da smo rijesili
## 
## FALSE 
##   101
##sta se desilo sa NA?



##Vise nema tih obzervacija u bazi
length(WHO$PrimarySchoolEnrollmentFemale)
## [1] 194
length(WHOPSEFnona$PrimarySchoolEnrollmentFemale) #manje za 93
## [1] 101