[英]Date iteration with Rcpp loop
For fastening purpose, i'm trying to convert a simple 'for loop' in R into a Rcpp one.出于紧固目的,我试图将 R 中的一个简单的“for 循环”转换为 Rcpp 循环。
I have a date vector named "date_vector" which is composed by X identical dates.我有一个名为“date_vector”的日期向量,它由 X 个相同的日期组成。 For each iteration of i, I add 1 minutes to the date_vector value.
对于 i 的每次迭代,我将 1 分钟添加到 date_vector 值。 The R 'for loop' (see below) works properly, but it is too slow for my very large dataset (2 years ~ 1million of rows).
R 'for 循环'(见下文)工作正常,但对于我非常大的数据集(2 年 ~ 100 万行)来说它太慢了。
I've read that Rccp could be a solution to speed up the loop.我读过 Rccp 可能是加速循环的解决方案。 However, I'm a 'Rcpp' noob and I'm struggling to convert my loop.
但是,我是一个“Rcpp”菜鸟,我正在努力转换我的循环。
Can someone help me and explain me the solution?有人可以帮助我并向我解释解决方案吗? Thank you very much.
非常感谢你。 Best wishes for 2023.
祝 2023 年一切顺利。
The orignial R Loop:原来的R循环:
for(i in 2:nrow(klines)){
date_vector[i] <- date_vector[i-1]+minutes(1)
}
My Rcpp loop attempt:我的 Rcpp 循环尝试:
cpp_update_date_vector <- cppFunction('DateVector fonction_test(DateVector zz),
int n = zz.size();
DateVector = date_vector;
for (int i = 0; i < n; i++) {
date_vector[i] = date_vector[i-1] + 60;
}
')
You can likely achieve your goal without a loop at all.您可能根本不需要循环就可以实现您的目标。 It sounds like you're trying to change a vector of identical datetimes to a sequence one minute apart, right?
听起来您正在尝试将相同日期时间的向量更改为相隔一分钟的序列,对吗? If so, you could do:
如果是这样,你可以这样做:
library(lubridate)
date_vector <- rep(ymd_hms("2020-01-01 12:00:00"), 10)
date_vector + minutes(seq_along(date_vector) - 1)
[1] "2020-01-01 12:00:00 UTC" "2020-01-01 12:01:00 UTC"
[3] "2020-01-01 12:02:00 UTC" "2020-01-01 12:03:00 UTC"
[5] "2020-01-01 12:04:00 UTC" "2020-01-01 12:05:00 UTC"
[7] "2020-01-01 12:06:00 UTC" "2020-01-01 12:07:00 UTC"
[9] "2020-01-01 12:08:00 UTC" "2020-01-01 12:09:00 UTC"
For completeness, here is how you would write the code in Rcpp:为了完整起见,以下是您在 Rcpp 中编写代码的方式:
cpp_update_date_vector <- Rcpp::cppFunction('
DatetimeVector fonction_test(DatetimeVector zz) {
for (int i = 1; i < zz.size(); i++) {
zz[i] = zz[i-1] + 60;
}
return zz;
}
')
But it is no faster then base R's seq
function, which can easily create a sequence of date-times 1 minute apart.但它并不比 base R 的
seq
function 快,后者可以轻松创建相隔 1 分钟的日期时间序列。 Here is a comparison of the two methods on a 1,000,000-length date-time vector.下面是对长度为 1,000,000 的日期时间向量的两种方法的比较。 Note that they are both comparable, and both considerably faster than using
lubridate
.请注意,它们具有可比性,并且都比使用
lubridate
。
microbenchmark::microbenchmark(
lubridate = big_vec + lubridate::minutes(seq_along(big_vec) - 1),
Rcpp = cpp_update_date_vector(big_vec),
base_R = seq(big_vec[1], by = "1 min", length = 1000000)
)
#> Unit: milliseconds
#> expr min lq mean median uq max neval cld
#> lubridate 1168.921 1203.845 1318.950 1215.465 1570.376 1691.765 100 b
#> Rcpp 3.733 3.770 8.742 3.799 3.909 467.236 100 a
#> base_R 2.172 2.338 3.167 2.407 2.484 40.222 100 a
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