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Dynamically select data frame columns using $ and a character value
...s a reproducible example below:
# set seed for reproducibility
set.seed(123)
df <- data.frame( col1 = sample(5,10,repl=T) , col2 = sample(5,10,repl=T) , col3 = sample(5,10,repl=T) )
# We want to sort by 'col3' then by 'col1'
sort_list <- c("col3","col1")
# Use 'do.call' to call order. Se...
ActiveRecord, has_many :through, and Polymorphic Associations
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162
There is a known issue with Rails 3.1.1 that breaks this functionality. If you are having this p...
Getting pids from ps -ef |grep keyword
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234
You can use pgrep as long as you include the -f options. That makes pgrep match keywords in th...
what is the unsigned datatype?
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answered Jul 23 '09 at 13:46
Martin v. LöwisMartin v. Löwis
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Use find command but exclude files in two directories
...s with ./scripts/
Testing the Solution:
$ mkdir a b c d e
$ touch a/1 b/2 c/3 d/4 e/5 e/a e/b
$ find . -type f ! -path "./a/*" ! -path "./b/*"
./d/4
./c/3
./e/a
./e/b
./e/5
You were pretty close, the -name option only considers the basename, where as -path considers the entire path =)
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how does multiplication differ for NumPy Matrix vs Array classes?
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127
The main reason to avoid using the matrix class is that a) it's inherently 2-dimensional, and b...
Difference between Xcode version (CFBundleShortVersionString) and build (CFBundleVersion)
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edited Jul 20 '12 at 17:36
answered Jul 30 '11 at 6:10
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Understanding how recursive functions work
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2
I'm not too happy with thinking of it as a copy. I find that a more intuitive explanation is to differentiate the function itself (the code,...
Finding row index containing maximum value using R
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See ?which.max
> which.max( matrix[,2] )
[1] 2
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How to get execution time in rails console?
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242
timing = Benchmark.measure { Post.all }
The various attributes of the object returned (Bench...