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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...
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.
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Filter rows which contain a certain string
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263
The answer to the question was already posted by the @latemail in the comments above. You can ...
Limiting floats to two decimal points
...
26 Answers
26
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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 ...
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...
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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Get distance between two points in canvas
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211
You can do it with pythagoras theorem
If you have two points (x1, y1) and (x2, y2)
then you c...