How do I insert a 2D array into another 2D array? (Ruby) - arrays

Question

I'm attempting to put an array of integers (eventually to be converted into their ASCII characters) into an array, framed by stars but it just isn't working and I don't know why.
My code is below and data is an array containing 40 columns and 22 rows.
image = Array.new(24) { Array.new(42, ' ')}
(0..23).each do |r|
if r == 0 || r == 23 then
(0..41).each do |c|
image[r][c] = '*'
end
else
(0..41).each do |c|
if c == 0 || c == 41 then
image[r][c] = '*'
else
image[r][c] = data[r][c]
end
end
end
end
print image

Answer 1

If I understand your case right and you have next values:
image = Array.new(5) { Array.new(10, ' ')}
data = [[0, 1, 2, 3, 4, 5, 6, 7], [8, 9, 10, 11, 12, 13, 14, 15], [16, 17, 18, 19, 20, 21, 22, 23]]
Then minimum edits of your code should looks like:
(0..4).each do |r|
(0..9).each do |c|
if r == 0 || r == 4 || c == 0 || c == 9
image[r][c] = '*'
else
image[r][c] = data[r.pred][c.pred]
end
end
end
Then result will looks like:
> image
#=> [["*", "*", "*", "*", "*", "*", "*", "*", "*", "*"], ["*", 0, 1, 2, 3, 4, 5, 6, 7, "*"], ["*", 8, 9, 10, 11, 12, 13, 14, 15, "*"], ["*", 16, 17, 18, 19, 20, 21, 22, 23, "*"], ["*", "*", "*", "*", "*", "*", "*", "*", "*", "*"]]

Answer 2

You're making this way too complicated. Break it up into steps. Remove the nested loops and conditionals.
1) Grab rows 0 and 23 out of image and set everything to "*".
2) Iterate through each row (ie image.each do |row| ...) and set columns 0 and 41 to "*".
3) Iterate again through each row and set the other columns to match what's in data (a nested loop is probably necessary here, no conditional though).
Edit: full code could look something like this:
#step0 -- create nested array with first and last rows missing. Doesn't need useless spaces. Nil instead.
image = Array.new(22) { Array.new(42) }
#step1 --- iterate through the rows and set first and last columns to "*"
image.each do |row|
row[0] = "*"
row[41] = "*"
end
#step2 -- add first and last rows, which are all "*"
image.shift(Array.new(42, "*"))
image.push(Array.new(42, "*"))
#step3 -- nested loop that matches image to data only if not already set.
image.each_with_index do |row, ridx|
row.each_with_index do |col, cidx|
image[row][col] = data[row][col] unless image[row][col]
end
end
It might actually just be easier to clone the data and then add that border to it. That is, after all, all you're doing here, and might be the source of the problem you're having.

Answer 3

Let's first construct data. For simplicity I assume data has 6 elements ("rows") and each element is an array of 4 elements (forming "columns", though Ruby actually has no concept of arrays having rows and columns).
ROWS = 6
COLS = 4
data = (ROWS*COLS).times.to_a.each_slice(4).to_a
#=> [[0, 1, 2, 3], [4, 5, 6, 7], [8, 9, 10, 11], [12, 13, 14, 15],
# [16, 17, 18, 19], [20, 21, 22, 23]]
Now we need only modify your code slightly to produce the desired result.
rows = data.size+2
#=> 8
cols = data.first+2
#=> 6
image = Array.new(rows) { Array.new(cols, ' ')}
(0...rows).each do |r| # note 3 dots here and below
if r == 0 || r == rows-1
(0...cols).each do |c|
image[r][c] = '*'
end
else
(0...cols).each do |c|
if c == 0 || c == cols-1
image[r][c] = '*'
else
image[r][c] = data[r-1][c-1]
end
end
end
end
image.each { |row| p row }
prints
["*", "*", "*", "*", "*", "*"]
["*", 0, 1, 2, 3, "*"]
["*", 4, 5, 6, 7, "*"]
["*", 8, 9, 10, 11, "*"]
["*", 12, 13, 14, 15, "*"]
["*", 16, 17, 18, 19, "*"]
["*", 20, 21, 22, 23, "*"]
["*", "*", "*", "*", "*", "*"]
A more Ruby-like way of doing this is as follows.
image = [['*']*(data.first.size+1)]
ROWS.times { |i| image << ['*', *data[i], '*'] }
image << image.first
image.each { |row| p row }
If you instead wanted to produce a nicely-formatted table, you could do the following.
def fmt(data, col_space, boundary_char='*')
col_width = data.flatten.map { |n| n.to_s.size }.max + col_space
nrows, ncols = data.size, data.first.size
header = boundary_char * (col_width * ncols + 2 + col_space)
right_border = " "*col_space << boundary_char
image = [header]
data.each { |row|
image << "%s%s%s" %
[boundary_char, row.map { |n| n.to_s.rjust(col_width) }.join, right_border] }
image << header
image
end
puts fmt(data, 2)
prints
********************
* 0 1 2 3 *
* 4 5 6 7 *
* 8 9 10 11 *
* 12 13 14 15 *
* 16 17 18 19 *
* 20 21 22 23 *
********************
The steps are as follows (data as defined above).
col_space = 2
boundary_char='*'
a = data.flatten
#=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
# 15, 16, 17, 18, 19, 20, 21, 22, 23]
b = a.map { |n| n.to_s.size }
#=> [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2]
col_width = b.max + col_space
#=> 2 + 2 => 4
nrows, ncols = data.size, data.first.size
#=> [6, 4]
header = boundary_char * (col_width * ncols + 2 + col_space)
#=> * * (4*4 + 2 + 2)
#=> "********************"
right_border = " "*col_space << boundary_char
#=> " "*2 << "*" =< " " << "*" => " *"
image = [header]
#=> ["********************"]
data.each { |row|
puts "row=#{row}"
puts " image row=#{"%s%s%s" % [boundary_char,
row.map { |n| n.to_s.rjust(col_width) }.join, right_border]}"
image << "%s%s%s" % [boundary_char,
row.map { |n| n.to_s.rjust(col_width) }.join, right_border] }
row=[0, 1, 2, 3]
image row=* 0 1 2 3 *
row=[4, 5, 6, 7]
image row=* 4 5 6 7 *
row=[8, 9, 10, 11]
image row=* 8 9 10 11 *
row=[12, 13, 14, 15]
image row=* 12 13 14 15 *
row=[16, 17, 18, 19]
image row=* 16 17 18 19 *
row=[20, 21, 22, 23]
image row=* 20 21 22 23 *
Then
image << header
image
returns the result above.