#Actividad de R

#install.packages()
library(dslabs)
data("movielens")
head(movielens)
##   movieId                                   title year
## 1      31                         Dangerous Minds 1995
## 2    1029                                   Dumbo 1941
## 3    1061                                Sleepers 1996
## 4    1129                    Escape from New York 1981
## 5    1172 Cinema Paradiso (Nuovo cinema Paradiso) 1989
## 6    1263                        Deer Hunter, The 1978
##                             genres userId rating  timestamp
## 1                            Drama      1    2.5 1260759144
## 2 Animation|Children|Drama|Musical      1    3.0 1260759179
## 3                         Thriller      1    3.0 1260759182
## 4 Action|Adventure|Sci-Fi|Thriller      1    2.0 1260759185
## 5                            Drama      1    4.0 1260759205
## 6                        Drama|War      1    2.0 1260759151
class(movielens)
## [1] "data.frame"
summary(movielens)
##     movieId          title                year     
##  Min.   :     1   Length:100004      Min.   :1902  
##  1st Qu.:  1028   Class :character   1st Qu.:1987  
##  Median :  2406   Mode  :character   Median :1995  
##  Mean   : 12549                      Mean   :1992  
##  3rd Qu.:  5418                      3rd Qu.:2001  
##  Max.   :163949                      Max.   :2016  
##                                      NA's   :7     
##                   genres          userId        rating        timestamp        
##  Drama               : 7757   Min.   :  1   Min.   :0.500   Min.   :7.897e+08  
##  Comedy              : 6748   1st Qu.:182   1st Qu.:3.000   1st Qu.:9.658e+08  
##  Comedy|Romance      : 3973   Median :367   Median :4.000   Median :1.110e+09  
##  Drama|Romance       : 3462   Mean   :347   Mean   :3.544   Mean   :1.130e+09  
##  Comedy|Drama        : 3272   3rd Qu.:520   3rd Qu.:4.000   3rd Qu.:1.296e+09  
##  Comedy|Drama|Romance: 3204   Max.   :671   Max.   :5.000   Max.   :1.477e+09  
##  (Other)             :71588
names(movielens)
## [1] "movieId"   "title"     "year"      "genres"    "userId"    "rating"   
## [7] "timestamp"
##TABLA SIN FECHAS NA

MovielensSinNa <- movielens[!is.na(movielens$year),]


length(MovielensSinNa$movieId)
## [1] 99997
length(movielens$movieId)
## [1] 100004
diferencia<-as.integer(length(MovielensSinNa$movieId))-as.integer(length(movielens$movieId))

print(paste("Hay", -diferencia, "películas con datos nulos")) 
## [1] "Hay 7 películas con datos nulos"
##Peores PELICULAS

promedioPuntaje <- 3.544

MovielensPeores <- MovielensSinNa[MovielensSinNa$rating < promedioPuntaje,]

print(paste("De", length(movielens$movieId), "Hay" , length(MovielensPeores$movieId), "por debajo del promedio de calificación (3.544)"))
## [1] "De 100004 Hay 48433 por debajo del promedio de calificación (3.544)"