时间戳

首页 > 解决方案 > R：在合并之前查找不匹配的列名

r - R：在合并之前查找不匹配的列名

问题描述

我有大量数据框要合并。每个都有数百列。我想在执行此操作之前识别所有不匹配的列名。到目前为止，我可以生成一个不匹配列表，但是格式很糟糕，我不太清楚如何判断它们来自哪个数据框。

#create data
df1 <- data.frame("col1" = 3:4, "Age" = c(22,16), "Name" = c("James","Jim"))
df2 <- data.frame("col1" = 3:4, "Age" = c(18,19), "Name" = c("Mike","Mia"))
df3 <- data.frame("mismatch_col_name_1" = 1:2, "Age" = c(21,15), "name" = c("John","Dora"))
df4 <- data.frame("mismatch_col_name_2" = 1:2, "Age" = c(21,15), "Name" = c("John","Dora"))
files <- list(df1, df2, df3, df4)

# find mismatched column names
mismatches <- NULL
for (i in 1:(length(files) - 1)) {
  mismatches <- c(mismatches, setdiff(colnames(files[[i]]), colnames(files[[i+1]])))
}
mismatches <- c(mismatches, setdiff(colnames(files[[length(files)]]), colnames(files[[1]])))
print(mismatches)

[1] "col1"                "Name"                "mismatch_col_name_1" "name"               
[5] "mismatch_col_name_2"

所需的输出将类似于：

“df3” “mismatch_col_name_1” “名称”

"df4" "mismatch_col_name_2" "名称"

甚至 df 名称和列号。对任何解决方案或更好的方法感兴趣。

标签： rmerging-data

解决方案

这是一种方法，可以让您找到一个列表（在 R 意义上），其中包含每个文件的不匹配项。它的前提是您知道用于比较每个文件的“真实”名称集。

lapply(files, function(x) {

    # vector of desired names
    master <- c('col1', 'Age', 'Name')

    # use 'match' to compare this df's names to the master. the order of the
    # cols won't matter; if the name in x appears in master, 'match' will return
    # an integer indicating the position of the col with that name in x.
    comparison <- match(names(x),  master)

    # if all col names in x appear in master, you get all integers, so: NULL
    if (!any(is.na(comparison))) {

        NULL

    # if names in x don't appear in master, you get an NA from 'match', so here you
    # create a vector of the names in x that aren't in master. You could also capture
    # their position here if that's helpful.
    } else {

        mismatches <- names(x)[which(is.na(comparison))]

    }

})

结果：

[[1]]
NULL

[[2]]
NULL

[[3]]
[1] "mismatch_col_name_1" "name"               

[[4]]
[1] "mismatch_col_name_2"

然后，您可以通过多种方式组织或总结此列表的内容，但这主要是格式问题。

推荐阅读