R 宏以启用类似于 SAS 中的 %let 的用户定义输入 [英] R macros to enable user defined input similar to %let in SAS

问题描述

我正在尝试自动化 R 中的特定过程，其中基本上代码保持不变，但导入的输入文件发生了变化 - 路径和大部分文件名相同，只有一个单词变化 - 并且某些变量名称发生变化.我想进行用户定义的这些更改:就像 SAS 中的 %let 一样.我可以用 &. 调用一个值.

I am trying to automate a particular process in R, where essentially the code remains the same but the input files imported change- the path and most of the file name is the same only one word changes- and certain variable names change. I would like to make these changes user defined: much like %let in SAS. where i can call a value with &.

例如，如果我有这个特定的导入代码:

For example if i have this particular import code:

Category_sales<- read.csv("C:/Projects/Consumption curves/UKPOV/excel files/MSP_product_CC_2009_salespercap.csv")

我只想根据用户的需要更改 MSP 这个词.在 SAS 中，我会定义一个宏变量，例如 %let metric=MSP

Where I would like only the word MSP to change depending on what the user wants. In SAS I would define a macrovariable like say %let metric=MSP

并将代码替换为

`C:/Projects/Consumption curves/UKPOV/excel files/&metric_product_CC_2009_salespercap.csv`

另外，如果我有一个变量说 MaxGNI 并且我希望只有 GNI 部分像 Max&econvar 那样由用户定义/替换，而我可以有 econvar 定义为 %let econvar= GNI 或任何其他指标.

Also If I have a variable say MaxGNI and I would like only the GNI part to be user defined/replaced like Max&econvar where I could have econvar defined as %let econvar= GNI or any other metric.

不过，我正在 R 中寻找类似的东西.

I am looking for something similar in R however.

推荐答案

您可以使用 paste0 函数完成此任务.

You can accomplish this task using the paste0 function.

metric <- "MSP"
infile <- paste0("C:/Projects/Consumption curves/UKPOV/excel files/",metric,"_product_CC_2009_salespercap.csv")
Category_sales <- read.csv(infile)

或封装在函数中

readCSV <- function(var) {
       metric <- var
       infile <- paste0("C:/Projects/Consumption curves/UKPOV/excel files/",metric,"_product_CC_2009_salespercap.csv")
       return(infile)

}

Category_sales <- read.csv(readCSV('MSP'))

您可以对字符串中需要替换的所有位应用相同的逻辑.

You can apply the same logic to all the bits that need to be replaced in your string.

关于变量名你可以这样做:

Regarding to variable names you can do:

eval(parse(....)) 将起作用

data1 <- data.frame(column1 = 1:10, column2 = letters[1:10])
txt <- "data1$column2"

> eval(parse(text = txt))
 [1] a b c d e f g h i j
Levels: a b c d e f g h i j

对于您的特定情况，您可以将 txt 替换为相同的 paste0 逻辑来构建变量名称.

For your particular case you can replace txt with the same paste0 logic to build your variable names.

此 SO Q/A

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