How to add vectors to the columns of some array in Julia?

Question

I know that, with package DataFrames, it is possible by doing simply

julia> df = DataFrame();

julia> for i in 1:3
          df[i] = [i, i+1, i*2]
       end

julia> df
3x3 DataFrame
|-------|----|----|----|
| Row # | x1 | x2 | x3 |
| 1     | 1  | 2  | 3  |
| 2     | 2  | 3  | 4  |
| 3     | 2  | 4  | 6  |

... but are there any means to do the same on an empty Array{Int64,2} ?

Answer 1

If you know how many rows you have in your final Array, you can do it using hcat:

# The number of lines of your final array
numrows = 3

# Create an empty array of the same type that you want, with 3 rows and 0 columns:
a = Array(Int, numrows, 0)

# Concatenate 3x1 arrays in your empty array:
for i in 1:numrows
    b = [i, i+1, i*2] # Create the array you want to concatenate with a
    a = hcat(a, b)
end

Notice that, here you know that the arrays b have elements of the type Int. Therefore we can create the array a that have elements of the same type.