Hi Everybody,
I am looking to do some basic statistics in ruby. Mean, Variance,
Standard deviation, etc. Does anyone know if there is a gem or a
library available for this?
More exactly, I want to take test scores for students and conver them to
A, B, C, D, F. In order to calculate Grade Point Averages.
Thank you,
peajoe
Hi,
I am brand new to ruby and liking it so far - particularly the watir test libraries. I am comfortable with the Java for loop syntax (i=0, i<4, i++) and haven't found something in ruby that feels as elegant, particularly when I want to use an increasing value i within the loop. Here's an example (with my limited ruby)
i=0
0.upto(3) do puts 'try number ' + i.to_s i = i+1 # is there a more elegant way to do i++ ?
end
I am guessing that ruby provides a more elegant way to do the above. I would love recommendations both on how to iterate when I want to use the changing value of the iterator in the loop, and how in ruby to do i++. Is there a way with upto() to use the current value during iteration? or another iterator where that is possible without needing to define i seperately?
Thanks in advance,
Jeff Fry
I have some code like this in the Production Log Analyzer, its pretty small
module Enumerable
On 30 Mar 2005, at 11:14, peajoe wrote:
Hi Everybody,
I am looking to do some basic statistics in ruby. Mean, Variance,
Standard deviation, etc. Does anyone know if there is a gem or a
library available for this?
##
# Sum of all the elements of the Enumerable
def sum
return self.inject(0) { |acc, i| acc + i }
end
##
# Average of all the elements of the Enumerable
#
# The Enumerable must respond to #length
def average
return self.sum / self.length.to_f
end
##
# Sample variance of all the elements of the Enumerable
#
# The Enumerable must respond to #length
def sample_variance
avg = self.average
sum = self.inject(0) { |acc, i| acc + (i - avg) ** 2 }
return (1 / self.length.to_f * sum)
end
##
# Standard deviation of all the elements of the Enumerable
#
# The Enumerable must respond to #length
def standard_deviation
return Math.sqrt(self.sample_variance)
end
end
And some tests:
class TestEnumerable < Test::Unit::TestCase
def test_sum
assert_equal 45, (1..9).sum
end
def test_average
# Ranges don't have a length
assert_in_delta 5.0, (1..9).to_a.average, 0.01
end
def test_sample_variance
assert_in_delta 6.6666, (1..9).to_a.sample_variance, 0.0001
end
def test_standard_deviation
assert_in_delta 2.5819, (1..9).to_a.standard_deviation, 0.0001
end
end
More exactly, I want to take test scores for students and conver them to
A, B, C, D, F. In order to calculate Grade Point Averages.
--
Eric Hodel - drbrain@segment7.net - http://segment7.net
FEC2 57F1 D465 EB15 5D6E 7C11 332A 551C 796C 9F04
peajoe wrote:
I am looking to do some basic statistics in ruby. Mean, Variance, Standard deviation, etc. Does anyone know if there is a gem or a library available for this?
You might want to have a look at the NArray library that is available from RAA: http://www.ir.isas.ac.jp/~masa/ruby/index-e.html
It offers a few statistical methods and is quite fast as it is written in C.
If you are running on a *nix friendly station, take a look at ruby-gsl
(http://raa.ruby-lang.org/project/ruby-gsl/\), which if I understand
correctly are the ruby bindings to the C gsl library.
Of course, this might be overkill for doing A/B/C/D/F grading ... but
I thought I'd point it out 
Matt
On Thu, 31 Mar 2005 04:14:44 +0900, peajoe <no_spam@invalid.net> wrote:
Hi Everybody,
I am looking to do some basic statistics in ruby. Mean, Variance,
Standard deviation, etc. Does anyone know if there is a gem or a
library available for this?More exactly, I want to take test scores for students and conver them to
A, B, C, D, F. In order to calculate Grade Point Averages.Thank you,
peajoe
In article <no_spam-7132D1.13101030032005@news1.east.earthlink.net>,
Hi Everybody,
I am looking to do some basic statistics in ruby. Mean, Variance,
Standard deviation, etc. Does anyone know if there is a gem or a
library available for this?More exactly, I want to take test scores for students and conver them to
A, B, C, D, F. In order to calculate Grade Point Averages.Thank you,
peajoe
Don't know if this will meet your needs, it's not fancy but it works for
me...
class SimpleStats
attr_reader :n, :sampleMean, :min, :max
def initialize
reset
end
def reset
@n = 0
@min = 1.0 / 0.0
@max = -@min
@sumsq = @sampleMean = @min / @min
end
def newObs(datum)
x = datum.to_f
@max = x if !@max || x > @max
@min = x if !@min || x < @min
@n += 1
if (@n > 1)
delta = x - sampleMean
@sampleMean += delta / @n
@sumsq += delta * (x - @sampleMean)
else
@sampleMean = x
@sumsq = 0.0
end
end
def sampleVariance
@sumsq / (@n - 1)
end
def stdDeviation
Math::sqrt sampleVariance
end
end
peajoe <no_spam@invalid.net> wrote:
Jeff Fry wrote:
Hi,
I am brand new to ruby and liking it so far - particularly the watir test libraries. I am comfortable with the Java for loop syntax (i=0, i<4, i++) and haven't found something in ruby that feels as elegant, particularly when I want to use an increasing value i within the loop. Here's an example (with my limited ruby)
i=0
0.upto(3) do
puts 'try
number ' + i.to_s i = i+1 # is there a more elegant way to do i++ ?
end
Try:
0.upto(3) do |i|
puts "try number #{i}"
end
I am guessing that ruby provides a more elegant way to do the above. I would love recommendations both on how to iterate when I want to use the changing value of the iterator in the loop, and how in ruby to do i++.
i+=1 is the easiest way to increment a number.
By the way: In many/most cases, you can iterate over a collection (e.g.
an array) without worrying about the index, using #each. If you want to
iterate over the same collection and you need the index, you can use
each_with_index.
HTH,
Hal
Hi --
Hi,
I am brand new to ruby and liking it so far - particularly the watir test libraries.
Welcome 
I am comfortable with the Java for loop syntax (i=0, i<4, i++) and haven't found something in ruby that feels as elegant, particularly when I want to use an increasing value i within the loop. Here's an example (with my limited ruby)
i=0
0.upto(3) do puts 'try number ' + i.to_s i = i+1 # is there a more elegant way to do i++ ?
endI am guessing that ruby provides a more elegant way to do the above. I would love recommendations both on how to iterate when I want to use the changing value of the iterator in the loop, and how in ruby to do i++. Is there a way with upto() to use the current value during iteration? or another iterator where that is possible without needing to define i seperately?
You need to pass an argument to your code block:
0.upto(3) do |i| puts "try number #{i}" end
or you could do:
4.times {|i| puts "try number #{i}" } # here I've used the {} block
# syntax, which is pretty
# common for same-line blocks
or even:
puts (0..3).map {|i| "try number #{i}" }
(iterating over a range, which you can do if the range uses integral
values)
For general-purpose incrementing, there's:
i += 1
(There's no ++ in Ruby because numbers are immediate values. So this:
i = 0
i++
would actually be the same as:
0++
which would cause all sorts of trouble
David
On Thu, 31 Mar 2005, Jeff Fry wrote:
--
David A. Black
dblack@wobblini.net
Jeff Fry wrote:
Hi,
I am brand new to ruby and liking it so far - particularly the watir test libraries. I am comfortable with the Java for loop syntax (i=0, i<4, i++) and haven't found something in ruby that feels as elegant, particularly when I want to use an increasing value i within the loop. Here's an example (with my limited ruby)
i=0
0.upto(3) do puts 'try number ' + i.to_s i = i+1 # is there a more elegant way to do i++ ?
end
how about this
0.upto(3) do |i|
puts 'try number ' + i.to_s
end
the upto method passes the current value into the block when calling it.
also another way of writing i++ is i += 1
I am guessing that ruby provides a more elegant way to do the above. I would love recommendations both on how to iterate when I want to use the changing value of the iterator in the loop, and how in ruby to do i++. Is there a way with upto() to use the current value during iteration? or another iterator where that is possible without needing to define i seperately?
hth
--
Mark Sparshatt
Yes! (Probably several.)
This is off the top of my head (and I'm a newbie) so I may get some syntax
wrong:
[0..3].each {|i| puts 'try number ' + i.to_s}
Randy Kramer
On Wednesday 30 March 2005 02:29 pm, Jeff Fry wrote:
i=0
0.upto(3) do
puts 'try number ' + i.to_s
i = i+1 # is there a
more elegant way to do i++ ?
end
Please don't hijack threads by using your reply button and replacing the subject. Sensible mailers such as yours add In-Reply-To and References headers that cause responses to your hijacking attempt to be intermixed with the original thread.
Modern mailers have 'new' buttons and address books for a reason.
PGP.sig (194 Bytes)
On 30 Mar 2005, at 11:29, Jeff Fry wrote:
[some stuff]
--
Eric Hodel - drbrain@segment7.net - http://segment7.net
FEC2 57F1 D465 EB15 5D6E 7C11 332A 551C 796C 9F04
Eric Hodel <drbrain@segment7.net> writes:
[some stuff]
Please don't hijack threads by using your reply button and replacing
the subject. Sensible mailers such as yours add In-Reply-To and
References headers that cause responses to your hijacking attempt to
be intermixed with the original thread.
Or, if you have to, remove that header line.
Modern mailers have 'new' buttons and address books for a reason.
I find myself often doing that, though.
On 30 Mar 2005, at 11:29, Jeff Fry wrote:
Eric Hodel - drbrain@segment7.net - http://segment7.net
--
Christian Neukirchen <chneukirchen@gmail.com> http://chneukirchen.org