How do I generate a list with a specified increment step

Question

How do I generate a vector with a specified increment step  e g  2   For example  how do I produce the following  0  2  4  6  8  10

User · Answer

The following example shows benchmarks for a few alternatives.

library(rbenchmark) # Note spelling: "rbenchmark", not "benchmark"
benchmark(seq(0,1e6,by=2),(0:5e5)*2,seq.int(0L,1e6L,by=2L))
##                     test replications elapsed  relative user.self sys.self
## 2          (0:5e+05) * 2          100   0.587  3.536145     0.344    0.244
## 1     seq(0, 1e6, by = 2)         100   2.760 16.626506     1.832    0.900
## 3 seq.int(0, 1e6, by = 2)         100   0.166  1.000000     0.056    0.096

In this case, seq.int is the fastest method and seq the slowest. If performance of this step isn't that important (it still takes < 3 seconds to generate a sequence of 500,000 values), I might still use seq as the most readable solution.

User · Answer

You can use scalar multiplication to modify each element in your vector     gt  r  lt - 0 10   gt  r  lt - r   2  gt  r    1   0  2  4  6  8 10 12 14 16 18 20   or    gt  r  lt - 0 10   2   gt  r    1   0  2  4  6  8 10 12 14 16 18 20

User · Answer

Executing seq 1  10  1  does what 1 10 does  You can change the last parameter of seq  i e  by  to be the step of whatever size you like    gt   a vector of even numbers  gt  seq 0  10  by 2    Explicitly specifying  by  only to increase readability   gt   1   0  2  4  6  8 10

[r] How do I generate a list with a specified increment step?

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