DataFrames

Selecting and transforming columns When selecting variables of a data frame, we do add : to indicate that it’s a variable name. Thus for example, if we want to select column with variable x, we use :x inside select(). First let’s construct some 500 by 3 dimensional data frame called df that contains three columns each of which has name of A, B, and C. using DataFrames df = DataFrame( A=1:2:1000, B= repeat(1:10, inner=50), C= 1:500) Each of below codes produces 500 by 1 dataframe, a data frame that only contains column A....

Taking a Subset We can subset a dataframe using index. For example we can subset specific columns and rows by following codes. # column subset (subset df to only include column A and C) df[:, [:A, :C]] # row subset (subset df to only include 1st, 3rd, and 5th rows) df[[1,3,5], :] We could also use some selectors such as Not, Between, Colsand All. Following code removes columns whose names match r"x"....

Create dataframe To create a dataframe, simply use DataFrame function after loding DataFrames.jl. Following code produces a dataframe composed of three variables, A, B, and C, each of which has 500 rows. Each row of column A increments by 2 starting from integer 1. Column B repeats 50 times of each integer starting from 1. Coumn C lists integers from 1 to 500. using DataFrames df = DataFrame(A=1:2:1000, B= repeat(1:10, inner=50), C= 1:500) first, last The first and last functions act as head and tail function in R, which allow us to view the first or the last couple of rows of the dataset....