[英]Converting uneven rows to columns with FasterCSV
我有一個CSV數據文件,其行可能有500多列,有些列少了很多。 我需要轉置它,以便每一行成為輸出文件中的一列。 問題是原始文件中的行可能並非都具有相同的列數,所以當我嘗試數組的轉置方法時,我得到:
`transpose':元素大小不同(12應該是5)(IndexError)
是否有替代的轉置適用於不均勻的陣列長度?
我會插入空值來填充矩陣中的空洞,例如:
a = [[1, 2, 3], [3, 4]]
# This would throw the error you're talking about
# a.transpose
# Largest row
size = a.max { |r1, r2| r1.size <=> r2.size }.size
# Enlarge matrix inserting nils as needed
a.each { |r| r[size - 1] ||= nil }
# So now a == [[1, 2, 3], [3, 4, nil]]
aa = a.transpose
# aa == [[1, 3], [2, 4], [3, nil]]
# Intitial CSV table data
csv_data = [ [1,2,3,4,5], [10,20,30,40], [100,200] ]
# Finding max length of rows
row_length = csv_data.map(&:length).max
# Inserting nil to the end of each row
csv_data.map do |row|
(row_length - row.length).times { row.insert(-1, nil) }
end
# Let's check
csv_data
# => [[1, 2, 3, 4, 5], [10, 20, 30, 40, nil], [100, 200, nil, nil, nil]]
# Transposing...
transposed_csv_data = csv_data.transpose
# Hooray!
# => [[1, 10, 100], [2, 20, 200], [3, 30, nil], [4, 40, nil], [5, nil, nil]]
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