Hi,
Being used to deal with Octave / Matlab, I'm a bit confused by Ruby structures (arrays, hashes, etc). I have this data file "data.dat" with 3 columns:
1.240000 9.990000e-01 1.290000e-06
1.550000 1.000000e+00 2.920000e-06
2.066000 1.002000e+00 8.360000e-06
2.480000 1.001000e+00 1.520000e-05
2.755000 1.001000e+00 2.210000e-05
3.099000 1.003000e+00 3.570000e-05
3.444000 1.003000e+00 3.240000e-05
3.542000 1.003000e+00 1.720000e-05
4.133000 1.001000e+00 1.430000e-05
4.959000 1.001000e+00 2.400000e-05
6.199000 1.001000e+00 4.720000e-05
8.265000 9.990000e-01 1.210000e-04
I would like to think of the columns as arrays "a", "b", "c", execute a loop along their indices, pick the values i want, and do something with them. What would be a sensible data structure for this?
I can read this datafile line by line using IO:readlines("data.dat"), but I cannot find a way to refer to one column in the array of strings generated.
Best regards,
baptiste
baptiste Auguié wrote:
Hi,
Being used to deal with Octave / Matlab, I'm a bit confused by Ruby structures (arrays, hashes, etc). I have this data file "data.dat" with 3 columns:
1.240000 9.990000e-01 1.290000e-06
1.550000 1.000000e+00 2.920000e-06
2.066000 1.002000e+00 8.360000e-06
2.480000 1.001000e+00 1.520000e-05
2.755000 1.001000e+00 2.210000e-05
3.099000 1.003000e+00 3.570000e-05
3.444000 1.003000e+00 3.240000e-05
3.542000 1.003000e+00 1.720000e-05
4.133000 1.001000e+00 1.430000e-05
4.959000 1.001000e+00 2.400000e-05
6.199000 1.001000e+00 4.720000e-05
8.265000 9.990000e-01 1.210000e-04
I would like to think of the columns as arrays "a", "b", "c", execute a loop along their indices, pick the values i want, and do something with them. What would be a sensible data structure for this?
I can read this datafile line by line using IO:readlines("data.dat"), but I cannot find a way to refer to one column in the array of strings generated.
In native Ruby, the only way to do that would be:
arr = [[0,1],[2,3],[4,5]]
arr.map{|a| a[0]}
# => [0,2,4]
If you can install rb-gsl (and it's probably a good idea if you're expecting to do matlab/octavey things), then there's the GSL::Matrix#column method which (as I understand it, not being a heavy GSL user) actually gives a reference into the original matrix, rather than copying to a new one as Array#map does.
···
--
Alex
baptiste Auguié wrote:
Hi,
Being used to deal with Octave / Matlab, I'm a bit confused by Ruby structures (arrays, hashes, etc). I have this data file "data.dat" with 3 columns:
I would like to think of the columns as arrays "a", "b", "c", execute a loop along their indices, pick the values i want, and do something with them. What would be a sensible data structure for this?
I can read this datafile line by line using IO:readlines("data.dat"), but I cannot find a way to refer to one column in the array of strings generated.
You can use String#split to split each line into an array of 3 numbers. If you want to use the array values as numbers, you'll need to use String#to_f as well to convert the strings to numeric values.
ri String#split
ri String#to_f
···
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Maybe something like this is what you're looking for:
<code>
data = DATA.readlines
rows = data.map do |row|
row.split(/\s+/).map { |elt| elt.to_f }
end
a, b, c = rows.transpose
p a, b, c
__END__
1.240000 9.990000e-01 1.290000e-06
1.550000 1.000000e+00 2.920000e-06
2.066000 1.002000e+00 8.360000e-06
2.480000 1.001000e+00 1.520000e-05
</code>
<result>
[1.24, 1.55, 2.066, 2.48]
[0.999, 1.0, 1.002, 1.001]
[1.29e-06, 2.92e-06, 8.36e-06, 1.52e-05]
</result>
Regards, Morton
···
On Jun 30, 2007, at 6:37 AM, baptiste Auguié wrote:
Being used to deal with Octave / Matlab, I'm a bit confused by Ruby structures (arrays, hashes, etc). I have this data file "data.dat" with 3 columns:
1.240000 9.990000e-01 1.290000e-06
1.550000 1.000000e+00 2.920000e-06
2.066000 1.002000e+00 8.360000e-06
2.480000 1.001000e+00 1.520000e-05
2.755000 1.001000e+00 2.210000e-05
3.099000 1.003000e+00 3.570000e-05
3.444000 1.003000e+00 3.240000e-05
3.542000 1.003000e+00 1.720000e-05
4.133000 1.001000e+00 1.430000e-05
4.959000 1.001000e+00 2.400000e-05
6.199000 1.001000e+00 4.720000e-05
8.265000 9.990000e-01 1.210000e-04
I would like to think of the columns as arrays "a", "b", "c", execute a loop along their indices, pick the values i want, and do something with them. What would be a sensible data structure for this?
I can read this datafile line by line using IO:readlines("data.dat"), but I cannot find a way to refer to one column in the array of strings generated.
Dear Baptiste,
I'd also recommend rb-gsl, but if you have trouble
installing from source, you can also use the Matrix
class from Ruby:
http://www.ruby-doc.org/stdlib/libdoc/matrix/rdoc/classes/Matrix.html
require "matrix"
a=Matrix.columns([[25, 93], [-1, 66]])
=> 25 -1
93 66
a.transpose
=> 25 93
-1 66
Best regards,
Axel
···
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Thanks everyone for your suggestions, it's good to know different options. This community is great!
Thanks,
baptiste
···
On 30 Jun 2007, at 13:42, Axel Etzold wrote:
Dear Baptiste,
I'd also recommend rb-gsl, but if you have trouble
installing from source, you can also use the Matrix
class from Ruby:
http://www.ruby-doc.org/stdlib/libdoc/matrix/rdoc/classes/Matrix.html
require "matrix"
a=Matrix.columns([[25, 93], [-1, 66]])
=> 25 -1
93 66
a.transpose
=> 25 93
-1 66
Best regards,
Axel
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