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Does the ternary operator exist in R?
... if-else is equivalent to ?:.
> a <- 1
> x <- if(a==1) 1 else 2
> x
[1] 1
> x <- if(a==2) 1 else 2
> x
[1] 2
The power of R is vectorization. The vectorization of the ternary operator is ifelse:
> a <- c(1, 2, 1)
> x <- ifelse(a==1, 1, 2)
> x
[1] 1 2 1
>...
How do I write stderr to a file while using “tee” with a pipe?
...s substitution and file redirection:
command > >(tee -a stdout.log) 2> >(tee -a stderr.log >&2)
Let's split it up and explain:
> >(..)
>(...) (process substitution) creates a FIFO and lets tee listen on it. Then, it uses > (file redirection) to redirect the STDO...
Grouping functions (tapply, by, aggregate) and the *apply family
... <- matrix(seq(1,16), 4, 4)
# apply min to rows
apply(M, 1, min)
[1] 1 2 3 4
# apply max to columns
apply(M, 2, max)
[1] 4 8 12 16
# 3 dimensional array
M <- array( seq(32), dim = c(4,4,2))
# Apply sum across each M[*, , ] - i.e Sum across 2nd and 3rd dimension
apply(M, 1, sum)
# Result ...
Why do enum permissions often have 0, 1, 2, 4 values?
Why are people always using enum values like 0, 1, 2, 4, 8 and not 0, 1, 2, 3, 4 ?
7 Answers
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scp (secure copy) to ec2 instance without password
I have an EC2 instance running (FreeBSD 9 AMI ami-8cce3fe5), and I can ssh into it using my amazon-created key file without password prompt, no problem.
...
Limiting floats to two decimal points
...
26 Answers
26
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How to get all possible combinations of a list’s elements?
... list with 15 numbers in, and I need to write some code that produces all 32,768 combinations of those numbers.
27 Answers...
Get distance between two points in canvas
...
211
You can do it with pythagoras theorem
If you have two points (x1, y1) and (x2, y2)
then you c...
How to drop rows of Pandas DataFrame whose value in a certain column is NaN
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12 Answers
12
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Numpy - add row to array
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122
What is X? If it is a 2D-array, how can you then compare its row to a number: i < 3?
EDIT a...