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Numbering rows within groups in a data frame
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284
Use ave, ddply, dplyr or data.table:
df$num <- ave(df$val, df$cat, FUN = seq_along)
or:
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Code equivalent to the 'let' keyword in chained LINQ extension method calls
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4 Answers
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How many GCC optimization levels are there?
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4 Answers
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jQuery posting JSON
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davidism
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answered Apr 6 '11 at 18:19
Kyle WildKyle ...
Convert UTC to local time in Rails 3
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edited Dec 1 '14 at 20:49
answered Mar 14 '11 at 15:23
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How to have Emacs auto-refresh all buffers when files have changed on disk?
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edited Jul 3 '12 at 17:41
Tim Cooper
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How to override the [] operator in Python?
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edited Mar 19 '19 at 4:05
nairboon
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answered Dec 24 '09 at 10:...
How to select rows from a DataFrame based on column values?
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4135
To select rows whose column value equals a scalar, some_value, use ==:
df.loc[df['column_nam...
Can I have multiple :before pseudo-elements for the same element?
...actively undergoing a rewrite in the guise of css-content-3 and css-pseudo-4. The bad news is that the multiple pseudo-elements feature is nowhere to be found in either specification, presumably owing, again, to lack of implementer interest.
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