对嵌套循环使用lapply [英] using lapply for nested loops

问题描述

我已经在 R 中学习了一些 lapply 魔术，但是还没有弄清楚如何替换嵌套循环-这也是可能的吗?

I have been learning a bit of lapply magic in R, but have not figured out how to replace nested loops -- is this also possible?

这是我的问题，还有嵌套循环的解决方案.

Here's my problem, and the nested-loop solution.

monCode <- c('F', 'G', 'H', 'J', 'K', 'M', 'N', 
        'Q', 'U', 'V', 'X', 'Z')
yearRange <- as.character(3:15)
yearRange[as.numeric(yearRange) < 10] <- as.character(paste0("0", yearRange[as.numeric(yearRange) < 10]))

outList <- vector()
for(Yr in yearRange) {
    for (mon in monCode) {
        outList <- c(outList, (paste0("IB", mon, Yr, " Comdty")))
    }
}

我该如何使用嵌套的 lapply 函数而不是嵌套的循环来做到这一点?

How would i do this using nested lapply functions, rather than nested loops?

预先感谢

推荐答案

不需要嵌套循环或嵌套lapply.

No need for nested loops or nested lapply.

使用 expand.grid 创建 monCode 和 yearRange 的所有组合，然后创建 do.call(sprintf，...)将它们串联起来

Use expand.grid to create all your combinations of monCode and yearRange then do.call(sprintf,...) to concatenate them

f <- expand.grid(monCode,yearRange)
outList <- do.call(sprintf, c(f, fmt = 'IB%s%s comdty'))

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