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Created January 11, 2012 14:35
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Kata Four: Data Munging
# Houston Ruby group solution for http://codekata.pragprog.com/2007/01/kata_four_data_.html
require 'rspec'
class CalculateSpread
def for_file(filename)
smallest_day, smallest_spread = nil, infinity
File.readlines(filename).each do |line|
next unless valid_line?(line)
line_params = parse_line(line)
day = line_params.fetch(:day)
this_spread = line_params.fetch(:spread)
if this_spread < smallest_spread
smallest_day = day
smallest_spread = this_spread
end
end
smallest_day
end
def parse_line(line)
raise ArgumentError.new "Invalid Line" unless valid_line?(line)
day, max, min = line.split(" ")
spread = max.to_i - min.to_i
{:day => day.to_i, :max => max.to_i, :min => min.to_i, :spread => spread}
end
def valid_line?(line)
line.strip[0].to_i > 0
end
def infinity
1.0/0
end
end
describe CalculateSpread do
let(:line_1) { " 1 88 59 74 53.8 0.00 F 280 9.6 270 17 1.6 93 23 1004.5"}
let(:invalid_line) {" mo 82.9 60.5 71.7 16 58.8 0.00 6.9 5.3" }
context "#parse_line" do
let(:parsed_results) { subject.parse_line(line_1) }
it "should calculate a spread given a valid line" do
parsed_results.fetch(:spread).should eq(29)
end
it "should return the max from a line" do
parsed_results.fetch(:max).should eq(88)
end
it "should return the min from a line" do
parsed_results.fetch(:min).should eq(59)
end
it "should return the day from a line" do
parsed_results.fetch(:day).should eq(1)
end
end
it "should know that a line is invalid" do
subject.valid_line?(invalid_line).should be_false
end
it "should know that a line is valid" do
subject.valid_line?(line_1).should be_true
end
it "should raise error if invalid line" do
lambda{
subject.spread_for_line(invalid_line)
}.should raise_error
end
end
(Unofficial, Preliminary Data). Source: <a
href="http://www.erh.noaa.gov/er/box/dailystns.html">www.erh.noaa.gov/er/box/dailystns.html</a>
<pre>
MMU June 2002
Dy MxT MnT AvT HDDay AvDP 1HrP TPcpn WxType PDir AvSp Dir MxS SkyC MxR MnR AvSLP
1 88 59 74 53.8 0.00 F 280 9.6 270 17 1.6 93 23 1004.5
2 79 63 71 46.5 0.00 330 8.7 340 23 3.3 70 28 1004.5
3 77 55 66 39.6 0.00 350 5.0 350 9 2.8 59 24 1016.8
4 77 59 68 51.1 0.00 110 9.1 130 12 8.6 62 40 1021.1
5 90 66 78 68.3 0.00 TFH 220 8.3 260 12 6.9 84 55 1014.4
6 81 61 71 63.7 0.00 RFH 030 6.2 030 13 9.7 93 60 1012.7
7 73 57 65 53.0 0.00 RF 050 9.5 050 17 5.3 90 48 1021.8
8 75 54 65 50.0 0.00 FH 160 4.2 150 10 2.6 93 41 1026.3
9 86 32* 59 6 61.5 0.00 240 7.6 220 12 6.0 78 46 1018.6
10 84 64 74 57.5 0.00 F 210 6.6 050 9 3.4 84 40 1019.0
11 91 59 75 66.3 0.00 H 250 7.1 230 12 2.5 93 45 1012.6
12 88 73 81 68.7 0.00 RTH 250 8.1 270 21 7.9 94 51 1007.0
13 70 59 65 55.0 0.00 H 150 3.0 150 8 10.0 83 59 1012.6
14 61 59 60 5 55.9 0.00 RF 060 6.7 080 9 10.0 93 87 1008.6
15 64 55 60 5 54.9 0.00 F 040 4.3 200 7 9.6 96 70 1006.1
16 79 59 69 56.7 0.00 F 250 7.6 240 21 7.8 87 44 1007.0
17 81 57 69 51.7 0.00 T 260 9.1 270 29* 5.2 90 34 1012.5
18 82 52 67 52.6 0.00 230 4.0 190 12 5.0 93 34 1021.3
19 81 61 71 58.9 0.00 H 250 5.2 230 12 5.3 87 44 1028.5
20 84 57 71 58.9 0.00 FH 150 6.3 160 13 3.6 90 43 1032.5
21 86 59 73 57.7 0.00 F 240 6.1 250 12 1.0 87 35 1030.7
22 90 64 77 61.1 0.00 H 250 6.4 230 9 0.2 78 38 1026.4
23 90 68 79 63.1 0.00 H 240 8.3 230 12 0.2 68 42 1021.3
24 90 88 84 67.5 0.00 H 350 8.5 010 14 6.9 74 48 1018.2
25 90 72 81 61.3 0.00 190 4.9 230 9 5.6 81 29 1019.6
26 97* 64 81 70.4 0.00 H 050 5.1 200 12 4.0 107 45 1014.9
27 91 72 82 69.7 0.00 RTH 250 12.1 230 17 7.1 90 47 1009.0
28 84 68 76 65.6 0.00 RTFH 280 7.6 340 16 7.0 100 51 1011.0
29 88 66 77 59.7 0.00 040 5.4 020 9 5.3 84 33 1020.6
30 90 45 68 63.6 0.00 H 240 6.0 220 17 4.8 200 41 1022.7
mo 82.9 60.5 71.7 16 58.8 0.00 6.9 5.3
</pre>
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