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Convert column classes in data.table
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105
For a single column:
dtnew <- dt[, Quarter:=as.character(Quarter)]
str(dtnew)
Classes ‘...
How to sort an array in descending order in Ruby
... Here's what I found out:
#!/usr/bin/ruby
require 'benchmark'
ary = []
1000.times {
ary << {:bar => rand(1000)}
}
n = 500
Benchmark.bm(20) do |x|
x.report("sort") { n.times { ary.sort{ |a,b| b[:bar] <=> a[:bar] } } }
x.report("sort reverse") { n.times ...
Why is SSE scalar sqrt(x) slower than rsqrt(x) * x?
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sqrtss gives a correctly rounded result. rsqrtss gives an approximation to the reciprocal, acc...
Does assignment with a comma work?
Why does aaa = 1,2,3 work and set the value of aaa to 1 ?
4 Answers
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Slicing of a NumPy 2d array, or how do I extract an mxm submatrix from an nxn array (n>m)?
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As Sven mentioned, x[[[0],[2]],[1,3]] will give back the 0 and 2 rows that match with the 1 and 3 columns while x[[0,2],[1,3]] will return the values x[0,1] and x[2,3] in an array.
There is a helpful function for doing the first example I gave, numpy.ix_....
Check if at least two out of three booleans are true
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How do I plot in real-time in a while loop using matplotlib?
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Get the week start date and week end date from week number
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MongoDB sort排序、index索引教程 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...排序，sort()方法可以通过参数指定排序的字段，并使用 1 和 -1 来指...MongoDB sort排序
在MongoDB中使用使用sort()方法对数据进行排序，sort()方法可以通过参数指定排序的字段，并使用 1 和 -1 来指定排序的方式，其中 1 为升序排列，-...