如何向Julia中的某些数组的列添加向量？ [英] How to add vectors to the columns of some array in Julia?

问题描述

我知道，使用包 DataFrames 可以通过简单地

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  |

...但是有空的 Array {Int64,2} ？

推荐答案

如果你知道你的最后一行有多少行数组，你可以使用 hcat ：

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

请注意，在这里，您知道数组 b 具有类型为 Int 的元素。因此，我们可以创建具有相同类型元素的数组 a 。

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.

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