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Creating an R dataframe row-by-row
...code in R.
If you can, allocate your entire data.frame up front:
N <- 1e4 # total number of rows to preallocate--possibly an overestimate
DF <- data.frame(num=rep(NA, N), txt=rep("", N), # as many cols as you need
stringsAsFactors=FALSE) # you don't know levels y...
How to remove a field completely from a MongoDB document?
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14 Answers
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It is more efficient to use if-return-return or if-else-return?
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201
Since the return statement terminates the execution of the current function, the two forms are e...
How to tell which commit a tag points to in Git?
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19 Answers
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type object 'datetime.datetime' has no attribute 'datetime'
...b/python2.6/lib-dynload/datetime.so'>
>>> datetime.datetime(2001,5,1)
datetime.datetime(2001, 5, 1, 0, 0)
But, if you import datetime.datetime:
>>> from datetime import datetime
>>> datetime
<type 'datetime.datetime'>
>>> datetime.datetime(2001,5,1) # ...
Efficiently updating database using SQLAlchemy ORM
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184
SQLAlchemy's ORM is meant to be used together with the SQL layer, not hide it. But you do have...
Guards vs. if-then-else vs. cases in Haskell
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122
From a technical standpoint, all three versions are equivalent.
That being said, my rule of t...
Making an array of integers in iOS
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160
You can use a plain old C array:
NSInteger myIntegers[40];
for (NSInteger i = 0; i < 40; ...
How to split data into training/testing sets using sample function
...row(mtcars))
## set the seed to make your partition reproducible
set.seed(123)
train_ind <- sample(seq_len(nrow(mtcars)), size = smp_size)
train <- mtcars[train_ind, ]
test <- mtcars[-train_ind, ]
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