刪除列中的值與其他數據集的列中的值不匹配的所有行

Question

我有兩個數據集（作爲數據框導入）。第一個數據框是染色體列表和染色體上的感興趣位置（Number，Qual和dt只是其他列）。數據框被稱爲SAM

Number Qual chr  leftPos  dt 
    3  0 chr1 4105086  255 
    4  16 chr1 4464364  255 
    5  16 chr1 4464390  255 
    6  16 chr1 9655049  255 
    7  16 chr1 9945004  255 
    etc 

第二個數據集（稱爲計數）包含沿着染色體染色體和立場，我感興趣的是：

Chr  Locus 
    chr1 4105086 
    chr1 4464364 

我想刪除SAM中的所有行是在計數中沒有Chr和Locus的相應組合。

輸出應該是這樣的：

Number Qual chr  leftPos  dt 
3   0 chr1  4105086  255 
4  16 chr1  4464364  255 

我不想合併，因爲我不想在原始數據集（SAM）我只是想基於第一數據集，以排除行額外列等。

Answer 1

看看這是你在找什麼

# sample data 
sam = structure(list(Number = 3:7, Qual = c(0L, 16L, 16L, 16L, 16L), 
    chr = structure(c(1L, 1L, 1L, 1L, 1L), .Label = "chr1", class = "factor"), 
    leftPos = c(4105086L, 4464364L, 4464390L, 9655049L, 9945004L 
    ), dt = c(255L, 255L, 255L, 255L, 255L)), .Names = c("Number", 
"Qual", "chr", "leftPos", "dt"), class = "data.frame", row.names = c(NA, 
-5L)) 

counts = structure(list(Chr = structure(c(1L, 1L), .Label = "chr1", class = "factor"), 
    Locus = c(4105086L, 4464364L)), .Names = c("Chr", "Locus" 
), class = "data.frame", row.names = c(NA, -2L)) 

library(dplyr) 
new_data = sam %>% filter(paste0(chr,"_",leftPos) %in% 
          with(counts, paste0(Chr,"_",Locus))) 
new_data 
# Number Qual chr leftPos dt 
# 1  3 0 chr1 4105086 255 
# 2  4 16 chr1 4464364 255 

或者作爲建議

new_data = merge(sam, counts, by.x=c("chr","leftPos"), by.y=c("Chr","Locus")) 
new_data = new_data[,c(3,4,1,2,5)] 
# Number Qual chr leftPos dt 
# 1  3 0 chr1 4105086 255 
# 2  4 16 chr1 4464364 255