通过 sapply 应用多个功能 [英] Applying multiple function via sapply

问题描述

我正在尝试复制在 sapply 中应用多个函数的解决方案 R-Bloggers 但我无法让它以所需的方式工作.我正在处理一个简单的数据集，类似于下面生成的数据集:

I'm trying to replicate solution on applying multiple functions in sapply posted on R-Bloggers but I can't get it to work in the desired manner. I'm working with a simple data set, similar to the one generated below:

require(datasets)
crs_mat <- cor(mtcars)

# Triangle function
get_upper_tri <- function(cormat){
  cormat[lower.tri(cormat)] <- NA
  return(cormat)
}

require(reshape2)
crs_mat <- melt(get_upper_tri(crs_mat))

我想替换 Var1 和 Var2 列中的一些文本值.下面的错误语法说明了我要实现的目标:

I would like to replace some text values across columns Var1 and Var2. The erroneous syntax below illustrates what I am trying to achieve:

crs_mat[,1:2] <- sapply(crs_mat[,1:2], function(x) {
 # Replace first phrase
 gsub("mpg","MPG",x), 
 # Replace second phrase
  gsub("gear", "GeArr",x)
 # Ideally, perform other changes
})

当然，代码在语法上不正确并且失败.总而言之，我想做以下事情:

Naturally, the code is not syntactically correct and fails. To summarise, I would like to do the following:

1. 遍历前两列中的所有值(Var1 和 Var2)，并通过 gsub 执行简单的替换.
2. 理想情况下，我希望避免定义单独的函数，如 linked 发布并保留所有内容in sapply 语法
3. 我不想要嵌套循环

1. Go through all the values in first two columns (Var1 and Var2) and perform simple replacements via gsub.
2. Ideally, I would like to avoid defining a separate function, as discussed in the linked post and keep everything within the sapply syntax
3. I don't want a nested loop

<小时>

我查看了此处和此处 但是，如果可能，我想避免使用 plyr.我也有兴趣替换列值而不是创建新列，我想避免指定任何列名.在处理我现有的数据框时，使用列号对我来说更方便.

---

I had a look at the broadly similar subject discussed here and here but, if possible, I would like to avoid making use of plyr. I'm also interested in replacing the column values not in creating new columns and I would like to avoid specifying any column names. While working with my existing data frame it is more convenient for me to use column numbers.

根据非常有用的评论，我试图实现的目标可以总结在下面的解决方案中:

Following very useful comments, what I'm trying to achieve can be summarised in the solution below:

fun.clean.columns <- function(x, str_width = 15) {
  # Make character
  x <- as.character(x)
  # Replace various phrases
  x <- gsub("perc85","something else", x)
  x <- gsub("again", x)
  x <- gsub("more","even more", x)
  x <- gsub("abc","ohmg", x)
  # Clean spaces
  x <- trimws(x)
  # Wrap strings
  x <- str_wrap(x, width = str_width)
  # Return object
  return(x)
}
mean_data[,1:2] <- sapply(mean_data[,1:2], fun.clean.columns)

我的 global.env 中不需要这个函数，所以我可以在此之后运行 rm 但更好的解决方案将涉及 squeezing这在 apply 语法中.

I don't need this function in my global.env so I can run rm after this but even nicer solution would involve squeezing this within the apply syntax.

推荐答案

我们可以使用 library(qdap) 中的 mgsub 来替换多个模式.在这里，我使用 lapply 循环第一列和第二列，并将结果分配回 crs_mat[,1:2].请注意，我使用 lapply 而不是 sapply 因为 lapply 保持结构完整

We can use mgsub from library(qdap) to replace multiple patterns. Here, I am looping the first and second column using lapply and assign the results back to the crs_mat[,1:2]. Note that I am using lapply instead of sapply as lapply keeps the structure intact

library(qdap)
crs_mat[,1:2] <- lapply(crs_mat[,1:2], mgsub, 
   pattern=c('mpg', 'gear'), replacement=c('MPG', 'GeArr'))

这篇关于通过 sapply 应用多个功能的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！