Generate a Repeating Sequence Based on Vector

Generate a repeating sequence based on vector

Use each argument:

rep(c(1027, 1028, 1030, 1032, 1037), each = 6)
#  [1] 1027 1027 1027 1027 1027 1027
#  [7] 1028 1028 1028 1028 1028 1028
# [13] 1030 1030 1030 1030 1030 1030
# [19] 1032 1032 1032 1032 1032 1032
# [25] 1037 1037 1037 1037 1037 1037

times argument:

rep(c(1027, 1028, 1030, 1032, 1037), times = 6)
#  [1] 1027 1028 1030 1032 1037
#  [6] 1027 1028 1030 1032 1037
# [11] 1027 1028 1030 1032 1037
# [16] 1027 1028 1030 1032 1037
# [21] 1027 1028 1030 1032 1037
# [26] 1027 1028 1030 1032 1037

Generate a vector of repeating values sequences, with a given number of occurrences of each value

You can do this by over-replicating the input, then removing surplus repetitions.

Edit: here is a solution with no looping:

% Repeat array to max number of possible repetitions
out = repmat( vals, 1, max(reps) ); 
% Implicit expansion (requires R2016b or newer, otherwise use bsxfun) to create
% matrix of reducing repetition count, then remove repeated values
% where this is <= 0, i.e. where there are no repetitions remaining.
out(reshape( reps' - (0:max(reps)-1), 1, [] ) <= 0) = [];

% Pre-R2016b version would be 
% out(reshape( bsxfun(@minus, reps', (0:max(reps)-1)), 1, [] ) <= 0) = [];

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Original: Requires a single loop, but over the input values not the output array so it's at least a short one...

vals = [1,2,3,4];
reps = [3,2,5,1];
out = repmat( vals, 1, max(reps) ); % repeat array to max number of possible repetitions
for ii = 1:numel(vals)
    % Remove elements which have appeared too many times
    out( out == vals(ii) & (cumsum(out==vals(ii)) > reps(ii)) ) = [];
end

Sort vector into repeating sequence when sequential values are missing R

We can create the order based on the sequence of 'x'

x[order(ave(x, x, FUN = seq_along))]
#[1] 1 2 3 1 2 3 1 2 2

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Or with rowid fromdata.table

library(data.table)
x[order(rowid(x))]
#[1] 1 2 3 1 2 3 1 2 2

Create a repeating vector sequence using named vector of counts

rep( resp, times = counts)

Use the base function rep

Repeating a repeated sequence

You can do it with a single rep call. The each and times parameters are evaluated sequentially with the each being done first.

rep(1:4, times=3, each=3)  # 'each' done first regardless of order of named parameters
#[1] 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4

R repeating sequence add 1 each repeat

We can use rep and add with the initial vector

v1 + rep(0:3, each = length(v1))
#[1] 1 2 3 4 2 3 4 5 3 4 5 6 4 5 6 7

Or using sapply

c(sapply(v1, `+`, 0:3))

Or using outer

c(outer(v1, 0:3, `+`))

data

v1 < 1:4

Generate sequence of repeating, ascending integers, using a list containing the number of repetitions for each, with thrust

You can do this purely with thrust, using an approach similar to yours.

1. Do a prefix sum on the input to determine size of result for step 2, and scatter indices for step 3
2. Create an output vector to hold the result
3. scatter ones to the appropriate locations in the output vector, given by the indices from step 1
4. do a prefix sum on the output vector.

Note that this method would have to be modified if the input reps vector is allowed to contain values of 0.

Here's a worked example:

$ cat t404.cu
#include <thrust/scan.h>
#include <thrust/device_vector.h>
#include <thrust/copy.h>
#include <thrust/iterator/constant_iterator.h>
#include <thrust/iterator/permutation_iterator.h>
#include <iostream>

int main(){

  int host_reps[] = {3, 2, 5, 1};
  int ds = sizeof(host_reps)/sizeof(int);
  thrust::device_vector<int> reps(host_reps, host_reps+ds);
  thrust::inclusive_scan(reps.begin(), reps.end(), reps.begin());
  thrust::device_vector<int> result(reps[reps.size()-1]);
  thrust::copy_n(thrust::constant_iterator<int>(1), reps.size()-1, thrust::make_permutation_iterator(result.begin(), reps.begin()));
  thrust::inclusive_scan(result.begin(), result.end(), result.begin());
  thrust::copy_n(result.begin(), result.size(), std::ostream_iterator<int>(std::cout, ","));
  std::cout << std::endl;
}
$ nvcc -o t404 t404.cu
$ ./t404
0,0,0,1,1,2,2,2,2,2,3,
$

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