My journey through the data science - by Karolina M'Goma

Let's assume that you want to take some random observations from your data set. Dplyr helps you with the function sample_n(). To make your code reproducible you seed the ID of a “random” set of values. You need to indicate number of rows you want to extract and specify if the rows should be replaced or not. To show you how it works I will use again mtcars dataset which is included in your base R program. Let's see first six rows of this data frame.  library(dplyr) data("mtcars") head(mtcars)                    mpg cyl disp  hp drat    wt  qsec vs am gear carb Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4 Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4 Datsun 710        22.8   4  108  93 3.85 2.320 18.61...

Today I would like to show examples of different ways you can join data frames. Let's define and display them first. In first data.frame I will collect some information's about certain. It will contain name, high and nationality. df1<-data.frame(name=c("Ania","Marek","Kamil","Joanna","Patrice"),high=c(178,190,175,168,175),nationality=c("polish","polish","polish","polish","french")) df1       name high nationality 1    Ania   178      polish 2   Marek   190      polish 3   Kamil   175      polish 4  Joanna   168      polish 5 Patrice   175      french In second data.frame I will put observation about other group, containing their name and weight. What does this two data.frame have in common  ? We can see that both contain column with the name of the person and what is more some person like Ania and Pat...