diff --git a/check_graphite.gemspec b/check_graphite.gemspec
index 2532fa2..756db5b 100644
--- a/check_graphite.gemspec
+++ b/check_graphite.gemspec
@@ -20,7 +20,7 @@ Gem::Specification.new do |s|
 
   # specify any dependencies here; for example:
   # s.add_development_dependency "rspec"
-  s.add_runtime_dependency "linear-regression"
+  s.add_runtime_dependency "linear-regression", "~> 0.0.2"
   s.add_runtime_dependency "nagios_check"
 
   s.add_development_dependency "rake"
diff --git a/lib/attime.rb b/lib/attime.rb
index be0b6c5..897288e 100644
--- a/lib/attime.rb
+++ b/lib/attime.rb
@@ -36,24 +36,26 @@ module CheckGraphite
     "year" => 365 * DAY,
     "years" => "year",
   }
-  EXPR = /([+-])?([0-9]*)(.*)/
+  EXPR = /^([+-])?([0-9.]*)(.*)$/
 
   def self.attime(text, time = Time.now)
     match = EXPR.match(text)
     raise "Unparseable time period #{text}" unless match
     sign, scalar, unit = match[1..3]
-    raise "Missing scalar in time #{text}" if scalar == ""
-    raise "Missing unit in #{text}" if unit == ""
-    time + Integer(scalar) * lookup(unit) * (sign == "-" ? -1 : 1)
+    raise "Missing scalar in time #{text}" if scalar.empty?
+    raise "Missing unit in #{text}" if unit.empty?
+    time + Float(scalar) * lookup(unit) * (sign == "-" ? -1 : 1)
   end
 
   private
 
   def self.lookup(unit)
     x = UNITS[unit.downcase]
-    raise "Bad unit #{unit}" unless x
-    if x.is_a? String
+    case x
+    when String
       lookup(x)
+    when nil
+      raise "Bad unit #{unit}"
     else
       x
     end
diff --git a/lib/check_graphite/projection.rb b/lib/check_graphite/projection.rb
index 722704d..3239626 100644
--- a/lib/check_graphite/projection.rb
+++ b/lib/check_graphite/projection.rb
@@ -7,8 +7,8 @@ module CheckGraphite
   module Projection
     def self.included(base)
       base.on '--projection FUTURE_TIMEFRAME', :default => '2days' do |timeframe|
-        options.send('processor=', method(:projected_value))
-        options.send('timeframe=', timeframe)
+        options.send(:processor=, method(:projected_value))
+        options.send(:timeframe=, timeframe)
       end
     end
 
diff --git a/spec/attime_spec.rb b/spec/attime_spec.rb
index c73ecb5..f49996e 100644
--- a/spec/attime_spec.rb
+++ b/spec/attime_spec.rb
@@ -1,17 +1,20 @@
 require 'attime'
 
-describe '#attime' do
+describe 'CheckGraphite.attime' do
   subject do |example|
     delta = example.metadata[:description_args][0]
-    CheckGraphite.attime(delta)
+    CheckGraphite.attime(delta, now)
   end
 
+  let(:now) { Time.now }
+
   def timedelta(n)
-    Time.now + n
+    now + n
   end
 
   it("10days") { should be_within(0.9).of(timedelta(10 * 86400)) }
   it("0days") { should be_within(0.9).of(timedelta(0)) }
+  it("1.5days") { should be_within(0.9).of(timedelta(1.5 * 86400)) }
   it("-10days") { should be_within(0.9).of(timedelta(-10 * 86400)) }
   it("5seconds") { should be_within(0.9).of(timedelta(5)) }
   it("5minutes") { should be_within(0.9).of(timedelta(5 * 60)) }
@@ -26,6 +29,7 @@ def timedelta(n)
   it(1) { expect { subject }.to raise_error(/string/i) }
   it("Something") { expect { subject }.to raise_error(RuntimeError) }
   it("1m") { expect { subject }.to raise_error(/bad unit/i) }
+  it("1day 1day") { expect { subject }.to raise_error(/bad unit/i) }
   it("10") { expect { subject }.to raise_error(/unit/) }
   it("month") { expect { subject }.to raise_error(/scalar/) }
 end
diff --git a/spec/projection_spec.rb b/spec/projection_spec.rb
index c429c5a..17d8edc 100644
--- a/spec/projection_spec.rb
+++ b/spec/projection_spec.rb
@@ -1,7 +1,7 @@
 require 'check_graphite/projection'
 require 'nagios_check'
 
-describe describe CheckGraphite::Projection do
+describe CheckGraphite::Projection do
   let :check do
     Class.new do
       attr_reader :values
@@ -10,7 +10,7 @@
     end.new
   end
 
-  describe 'primary value' do
+  describe 'when looking at the primary value' do
     subject do
       check.prepare
       check.send(:parse_options, ['--projection', projection])
@@ -33,7 +33,7 @@
     end
   end
 
-  describe 'p-value' do
+  describe 'when looking at the p-value' do
     subject do
       check.prepare
       check.send(:parse_options, ['--projection', projection])
@@ -54,27 +54,27 @@
       it { should eq("1.0") }
     end
   end
+end
 
-  describe 'integration test' do
-    before do
-      FakeWeb.register_uri(
-        :get, "http://your.graphite.host/render?target=collectd.somebox.load.load.midterm&from=-30seconds&format=json",
-        :body => '[{"target": "collectd.somebox.load.load.midterm", "datapoints": [[1.0, 1339512060], [2.0, 1339512120], [6.0, 1339512180], [7.0, 1339512240]]}]',
-        :content_type => "application/json"
-      )
-    end
+describe 'when invoking graphite with --projection' do
+  before do
+    FakeWeb.register_uri(
+      :get, "http://your.graphite.host/render?target=collectd.somebox.load.load.midterm&from=-30seconds&format=json",
+      :body => '[{"target": "collectd.somebox.load.load.midterm", "datapoints": [[1.0, 1339512060], [2.0, 1339512120], [6.0, 1339512180], [7.0, 1339512240]]}]',
+      :content_type => "application/json"
+    )
+  end
 
-    it 'should output value, projection interval and p-value' do
-      stub_const("ARGV", %w{
-        -H http://your.graphite.host/render
-        -M collectd.somebox.load.load.midterm
-        -c 0:10
-        --projection 5min
-        --name ze-name
-      })
-      c = CheckGraphite::Command.new
-      STDOUT.should_receive(:puts).with(match(/ze-name.*in 5min.*p-value=0.9/))
-      lambda { c.run }.should raise_error SystemExit
-    end
+  it 'outputs value, projection interval and p-value' do
+    stub_const("ARGV", %w{
+      -H http://your.graphite.host/render
+      -M collectd.somebox.load.load.midterm
+      -c 0:10
+      --projection 5min
+      --name ze-name
+    })
+    c = CheckGraphite::Command.new
+    STDOUT.should_receive(:puts).with(match(/ze-name.*in 5min.*p-value=0.9/))
+    lambda { c.run }.should raise_error SystemExit
   end
 end