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In a javascript array, how do I get the last 5 elements, excluding the first element?
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You can call:
arr.slice(Math.max(arr.length - 5, 1))
If you don't want to exclude the first element, use
arr.slice(Math.max(arr.length - 5, 0))
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How to succinctly write a formula with many variables from a data frame?
...in a formula to mean all the variables, it is the . identifier.
y <- c(1,4,6)
d <- data.frame(y = y, x1 = c(4,-1,3), x2 = c(3,9,8), x3 = c(4,-4,-2))
mod <- lm(y ~ ., data = d)
You can also do things like this, to use all variables but one (in this case x3 is excluded):
mod <- lm(y ~ ...
Underscore: sortBy() based on multiple attributes
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11 Answers
11
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SQL MAX of multiple columns?
How do you return 1 value per row of the max of several columns:
22 Answers
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How to count the number of true elements in a NumPy bool array
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>>> import numpy as np
>>> boolarr = np.array([[0, 0, 1], [1, 0, 1], [1, 0, 1]], dtype=np.bool)
>>> boolarr
array([[False, False, True],
[ True, False, True],
[ True, False, True]], dtype=bool)
>>> np.sum(boolarr)
5
Of course, that is a bool...
Redirect Windows cmd stdout and stderr to a single file
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1111
You want:
dir > a.txt 2>&1
The syntax 2>&1 will redirect 2 (stderr) to 1 ...
Error: “dictionary update sequence element #0 has length 1; 2 is required” on Django 1.4
I have an error message on django 1.4:
12 Answers
12
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Finding duplicates in O(n) time and O(1) space
Input: Given an array of n elements which contains elements from 0 to n-1, with any of these numbers appearing any number of times.
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Scala @ operator
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It enables one to bind a matched pattern to a variable. Consider the following, for instance:
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How is a CRC32 checksum calculated?
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The polynomial for CRC32 is:
x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 ...