Ruby adding empty strings to hash for CSV spacing - ruby

Question

I have:
hash = {"1"=>["A", "B", "C", ... "Z"], "2"=>["B", "C"], "3"=>["A", "C"]
My goal is to use hash as a source for creating a CSV with columns whose names are a letter of the alphabet and with rows hash(key) = 1,2,3 etc.
I created an array of all hash.values.unshift("")values that serve as row 1 (columns labels).
desired output:
| A | B | C | ... | Z |
1| A | B | C | ... | Z |
2| | B | C | ....... |
3| A | | C | ....... |
Creating CSV:
CSV.open("groups.csv", 'w') do |csv|
csv << row1
hash.each do |v|
csv << v.flatten
end
end
This makes the CSV look almost what I want but There is no spacing to get columns to align.
Any advice on how to make a method for modifying my hash that compares my all [A-Z] against each subsequent hash key (rows) to insert empty strings to provide spacing?
Can Class CSV do it better?

Answer 1

Something like this?
require 'csv'
ALPHA = ('A'..'Z').to_a.freeze
hash={"1"=>ALPHA, "2"=>["B", "C"], "3"=>["A", "C"]}
csv = CSV.generate("", col_sep: "|") do |csv|
csv << [" "] + ALPHA # header
hash.each do |k, v|
alphabet = ALPHA.map { |el| [el, 0] }.to_h
v.each { |el| alphabet[el] += 1 }
csv << [k, *alphabet.map { |k, val| val == 1 ? k : " " }]
end
end
csv.split("\n").each { |row| puts row }
output:
|A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z
1|A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z
2| |B|C| | | | | | | | | | | | | | | | | | | | | | |
3|A| |C| | | | | | | | | | | | | | | | | | | | | | |

Answer 2

If your values are truly single characters and don't need the CSV escaping, then I recommend bypassing CSV altogether and building the string in plain Ruby.
Assuming you want to align your lines correctly regardless of the number of digits in the row number (e.g. 1, 10, and 100), you can use printf style formatting to guarantee horizontal aligment (assuming your row number width never exceeds the value of ROWNUM_WIDTH).
By the way, I changed the hash's keys to integers, hope that's ok.
#!/usr/bin/env ruby
FIELDS = ('A'..'Z').to_a
DATA = { 1 => FIELDS, 2 => %w(B C), 3 => %w(A C) }
ROWNUM_WIDTH = 3
output = ' ' * ROWNUM_WIDTH + " | #{FIELDS.join(' | ')} |\n"
DATA.each do |rownum, values|
line = "%*d | " % [ROWNUM_WIDTH, rownum]
FIELDS.each do |field|
char = values.include?(field) ? field : ' '
line << "#{char} | "
end
output << line << "\n"
end
puts output
=begin
Outputs:
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
1 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
2 | | B | C | | | | | | | | | | | | | | | | | | | | | | | |
3 | A | | C | | | | | | | | | | | | | | | | | | | | | | | |
=end

Answer 3

all = [*?A..?Z]
hash = {"1"=>[*?A..?Z], "2"=>["B", "C"], "3"=>["A", "C"]}
hash.map do |k, v|
[k, *all.map { |k| v.include?(k) ? k : ' ' }]
end.unshift([' ', *all]).
map { |row| row.join('|') }
#⇒ [
# [0] " |A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z",
# [1] "1|A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z",
# [2] "2| |B|C| | | | | | | | | | | | | | | | | | | | | | | ",
# [3] "3|A| |C| | | | | | | | | | | | | | | | | | | | | | | "
# ]