对于循环和gsub R [英] For loop and gsub R

问题描述

我对在R的for循环中使用gsub有一个疑问.

I have a question about having a gsub in a for loop in R.

我有一个带有"sku"和"cat"列的数据框(目录)，它们是来自不同来源的同一产品的sku ID和商品目录ID.

I have a dataframe (catalog) with "sku" and "cat" columns, they are a sku ID and a Catalog ID for the same product from different sources.

然后我有了一个带有sku的数据框( image_data )和图像说明(image_data).

I then have a dataframe (image_data) with sku, and image descriptions (image_data).

我想创建一个新列( new_image_description )，其中sku的所有实例都替换为 image_des 列中的相应目录号(请参见下面的内容).

I want to create a new column(new_image_description) where all instances of sku's is replaced by the corresponding catalog number (see bellow) from the column image_des.

但只能替换部分，而不能替换. 下面是一些虚拟数据.

But only replaces some and other not. bellow is some dummy data.

    catalog <- data.frame(sku = c('AX1', "BX2", "CX2", "DXX"), 
    cat = c("AL1", "AL2", "AL3", "AL4"))


    image_data <- data.frame(sku = c("CX2", "AX1", "BX2"), 
image_des = c("CX2 is a good product", "AX1 is not bad",  "BX2 is great as well as DXX"))

    image_data$new_image_description <- NA

    for (i in 1:nrow(catalog)) {

      image_data$new_image_description <-  gsub(as.character(catalog$sku[i]), as.character(catalog$cat[i]), image_data$image_des)

    }

我希望能提供任何可以解释为什么它不能替代sku的输入.

I would appreciate any input that can explain why it does not substitute the sku.

如果我单独进行，它会起作用.

If I do it individually it works.

对所有人最好

推荐答案

您可以使用 qdap::mgsub 以执行多个搜索和替换操作:

You may use qdap::mgsub to perform multiple search and replace operations:

多个Gsub
gsub 包含搜索字词向量和替换向量或单个值.

Multiple Gsub
A wrapper for gsub that takes a vector of search terms and a vector or single value of replacements.

请参阅R演示

> library(qdap)
> image_data$new_image_description <- mgsub(as.character(catalog$sku), as.character(catalog$cat), image_data$image_des)
> image_data
  sku                   image_des       new_image_description
1 CX2       CX2 is a good product       AL3 is a good product
2 AX1              AX1 is not bad              AL1 is not bad
3 BX2 BX2 is great as well as DXX AL2 is great as well as AL4

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