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Float vs Decimal in ActiveRecord
...a Float. It's like a scientific notation for binary (something like +1.43*10^2). Because of that, it is impossible to store fractions and decimals in Float exactly.
That's why there is a Decimal format. If you do this:
irb:001:0> "%.47f" % (1.0/10)
=> "0.100000000000000005551115123125782702...
How do I select elements of an array given condition?
...
answered Jun 13 '10 at 0:50
jfsjfs
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C# equivalent to Java's charAt()?
...
201
You can index into a string in C# like an array, and you get the character at that index.
Exam...
What do 'real', 'user' and 'sys' mean in the output of time(1)?
...
2130
Real, User and Sys process time statistics
One of these things is not like the other. Real ref...
Relative frequencies / proportions with dplyr
...n = n()) %>%
mutate(freq = n / sum(n))
# am gear n freq
# 1 0 3 15 0.7894737
# 2 0 4 4 0.2105263
# 3 1 4 8 0.6153846
# 4 1 5 5 0.3846154
From the dplyr vignette:
When you group by multiple variables, each summary peels off one level of the grouping. That makes ...
Read a zipped file as a pandas DataFrame
...long form:
df = pd.read_csv('filename.zip', compression='zip', header=0, sep=',', quotechar='"')
Description of the compression argument from the docs:
compression : {‘infer’, ‘gzip’, ‘bz2’, ‘zip’, ‘xz’, None}, default ‘infer’
For on-the-fly decompression of on-d...
What is the difference between String.slice and String.substring?
...nts.
If either argument is negative or is NaN, it is treated as if it were 0.
Distinctions of slice():
If start > stop, slice() will return the empty string. ("")
If start is negative: sets char from the end of string, exactly like substr() in Firefox. This behavior is observed in both Firefo...
List of installed gems?
... Gem::Requirement.default)
specs = Gem.source_index.search(dep)
puts specs[0..5].map{ |s| "#{s.name} #{s.version}" }
# >> Platform 0.4.0
# >> abstract 1.0.0
# >> actionmailer 3.0.5
# >> actionpack 3.0.5
# >> activemodel 3.0.5
# >> activerecord 3.0.5
Here's an ...
add a string prefix to each value in a string column using Pandas
...['col'].astype(str)
Example:
>>> df = pd.DataFrame({'col':['a',0]})
>>> df
col
0 a
1 0
>>> df['col'] = 'str' + df['col'].astype(str)
>>> df
col
0 stra
1 str0
share
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Regex to remove all (non numeric OR period)
I need for text like "joe ($3,004.50)" to be filtered down to 3004.50 but am terrible at regex and can't find a suitable solution. So only numbers and periods should stay - everything else filtered. I use C# and VS.net 2008 framework 3.5
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