Basic functions of working with tables

In this example, let's look at working with tables using the library. DataFrames.jl in the Engee environment.

Creating a table

Let's define a table and use it to consider working with functions.

One of the ways to set a task is to get it from an existing matrix.

x = rand(3,4) # We set the 3x4 matrix

3×4 Matrix{Float64}:
 0.926038   0.804963   0.534224    0.79081
 0.0455585  0.247521   0.00657984  0.944393
 0.560838   0.0451912  0.272253    0.225811

# Connecting the library to work
using DataFrames

y = DataFrame( x, ["A", "B", "C", "D"] )

You can set column names automatically by specifying the keyword in the second parameter. :auto.

y1 = DataFrame( x, :auto )

Functions for working with rows and columns

To display, for example, the second column of the table, you can access it with a dot by the column name or display all the rows of the second column. These two methods are shown in the cells with the code below.

y.B # Accessing through the column name

3-element Vector{Float64}:
 0.8049630878241182
 0.24752121054936527
 0.04519118103988562

y[:,2] # Output all rows of the 2nd column

3-element Vector{Float64}:
 0.8049630878241182
 0.24752121054936527
 0.04519118103988562

You can also output all but one column, for example С.

select(y[:,:], Not("C"))

To rename columns, there is a function rename(). The first argument of the function is the table, and the second is the new column names.

rename!(y1, ["A", "B", "C", "D"])

Column values can be sorted using the function sort().

sort!(y1.C) # We sorted the values in column C and recorded the result in the source table.

3-element Vector{Float64}:
 0.006579837672216482
 0.2722532183791443
 0.534224047073746

You can add a column to a table by referring to it by name and assigning a value. If there is no column with that name in the table, a new one will be created.

y1.F = 3 * (y1.B + y1.C) # Let's write in a new column the result of the sum of the values of columns A and B, multiplied by 3
y1

Thus, we have reviewed the basic basic functions of working with tables using the library. DataFrames.jl. For more information on working with tables, see DataFrames.jl.

	A	B	C	D
	Float64	Float64	Float64	Float64
1	0.926038	0.804963	0.534224	0.79081
2	0.0455585	0.247521	0.00657984	0.944393
3	0.560838	0.0451912	0.272253	0.225811