CODEWITHSUNDEEP
ruby
Leonard
Leonard

Reputation: 3208

Ruby to_f is returning nothing or 0.0

String to float conversion using to_f is not working for me.

I'm trying pick a column from the longitude and latitude data as below.

"136.98355","35.130433333333336","2013-07-31T22:37:12+09:00","2346","13066","42","0","0","0"
"136.98363333333333","35.1306","2013-07-31T22:38:13+09:00","1311","13580","41","0","0","0"
"136.98361666666668","35.130583333333334","2013-07-31T22:39:13+09:00","3946","13580","41","0","0","0"

When I simply grab the column using the below code, it works.

ruby -e "STDIN.readlines.each do |line| col = line.chomp.split(','); puts col[0] end" < new.csv > picked_nagoya.csv

Result:

"136.98355"
"136.98363333333333"
"136.98361666666668"

But when I apply to_f to convert strings into floats, the file picked_nagoya.csv is empty.

I tried to work it around by storing converted string into a variable and then writing it out to the file. However, it then returns 0.0s.

ruby -e "STDIN.readlines.each do |line| col = line.chomp.split(','); f =  col[0].to_f; puts f end" < new.csv > picked_nagoya.csv

Result:

0.0
0.0
0.0

What am I doing wrong here?

Upvotes: 0

Views: 521

Answers (2)

tadman
tadman

Reputation: 211570

Using the Ruby CSV parser you can extract the data and work with this:

require 'csv'

CSV.readlines('data.csv').each do |row|
  lat, lng = row.first(2).map(&:to_f)

  p [ lat, lng ]
end

Gives you output like:

[136.98355, 35.130433333333336]
[136.98363333333333, 35.1306]
[136.98361666666668, 35.130583333333334]

Upvotes: 1

Syntactic Fructose
Syntactic Fructose

Reputation: 20076

It's because to_f is expecting a number, but the first character of the string you're trying to convert is actually a quotation mark: "123.456"

You'll need to trim the quotes off the string before you do any conversion:

f = col[0].delete_prefix('"').delete_suffix('"').to_f

Upvotes: 2

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