r语言 - 如果在另一列中找不到列名，则删除列

Question

我有一个看起来与下面类似的数据帧。

set.seed(12)
size <- sample(100:1000, 7)
var <- c("V3", "V4", "V5", "V6", "V7", "V8", "V9")
dist <- matrix(runif(100), nrow = 7, ncol = 7)
diag(dist) <- 0
df <- as.data.frame(cbind(var, size, dist))

这导致了一个看起来像这样的数据集：

var size                  V3                V4                 V5                V6                V7                 V8                V9
1  V3  549                   0 0.264918377622962  0.787836347473785 0.439429325051606 0.941087544662878   0.97763589094393 0.774718186818063
2  V4  445  0.0228777434676886                 0 0.0978530396241695 0.669819295872003 0.693911424372345  0.197649595327675 0.394586439244449
3  V5  435 0.00832482660189271 0.457607151241973                  0 0.240883231163025 0.843702238984406  0.844225987326354 0.361513090785593
4  V6  346   0.392697197152302 0.540707547217607  0.217823043232784                 0 0.384644460165873 0.0950279189273715 0.421090044546872
5  V7  958   0.813880559289828 0.665679829893634  0.267943592974916 0.882756386883557                 0  0.381151003297418 0.322011524345726
6  V8  273    0.37624845537357 0.112698937533423  0.504767951788381 0.814063254510984  0.58848182996735                  0 0.552160830702633

我想删除在变量var中找不到列名的列(在本例中是名称为V9的列(。我还想保留前两列var和size。这导致一个数据集看起来像这样：

var size                  V3                V4                 V5                V6                V7                 V8
1  V3  549                   0 0.264918377622962  0.787836347473785 0.439429325051606 0.941087544662878   0.97763589094393 
2  V4  445  0.0228777434676886                 0 0.0978530396241695 0.669819295872003 0.693911424372345  0.197649595327675 
3  V5  435 0.00832482660189271 0.457607151241973                  0 0.240883231163025 0.843702238984406  0.844225987326354 
4  V6  346   0.392697197152302 0.540707547217607  0.217823043232784                 0 0.384644460165873 0.0950279189273715 
5  V7  958   0.813880559289828 0.665679829893634  0.267943592974916 0.882756386883557                 0  0.381151003297418 
6  V8  273    0.37624845537357 0.112698937533423  0.504767951788381 0.814063254510984  0.58848182996735                  0 

Answer 1

使用%in%查找要保留的变量，然后用TRUE手动替换前两个值。

col.keep <- colnames(df) %in% df$var
col.keep[1:2] <- TRUE
df2 <- df[col.keep]

如果您不知道df$var和df$size的位置，请手动将它们绑定到.中

col.keep <- colnames(df) %in% df$var
df3 <- cbind(df$var, df$size, df[col.keep])

Answer 2

查看pivot_longer，并将列V*放入行中。然后，您可以只筛选这些列并返回。