Sql 在R中选择表内行的快速方法?
我正在寻找一种从更大的表中提取大量行的快速方法。我的桌面如下:Sql 在R中选择表内行的快速方法?,sql,r,row,data.table,sqldf,Sql,R,Row,Data.table,Sqldf,我正在寻找一种从更大的表中提取大量行的快速方法。我的桌面如下: > head(dbsnp) snp gene distance rs5 rs5 KRIT1 1 rs6 rs6 CYP51A1 1 rs7 rs7 LOC401387 1 rs8 rs8 CDK6 1 rs9 rs9 CDK6 1 rs10 rs10 CDK6
> head(dbsnp)
snp gene distance
rs5 rs5 KRIT1 1
rs6 rs6 CYP51A1 1
rs7 rs7 LOC401387 1
rs8 rs8 CDK6 1
rs9 rs9 CDK6 1
rs10 rs10 CDK6 1
尺寸:
> dim(dbsnp)
[1] 11934948 3
我想选择列表中包含行名的行:
> head(features)
[1] "rs1367830" "rs5915027" "rs2060113" "rs1594503" "rs1116848" "rs1835693"
> length(features)
[1] 915635
毫不奇怪,这样做的简单方法花费了相当长的时间
我一直在研究通过R中的sqldf包实现这一点的方法。我认为这可能会更快。不幸的是,我不知道如何在SQL中选择具有特定行名的行
谢谢。大多数人最初尝试的方式是:
dbsnp[ rownames(dbsnp) %in% features, ] # which is probably slower than your code
因为您说这需要很长时间,所以我怀疑您已经超过了RAM容量,并且已经开始使用虚拟内存。您应该关闭系统,然后以R作为运行应用程序重新启动,看看是否可以避免“虚拟化”。使用
sqldf
您需要rownames=TRUE
,然后您可以使用row\u names
查询行名:
library(sqldf)
## input
test<-read.table(header=T,text=" snp gene distance
rs5 rs5 KRIT1 1
rs6 rs6 CYP51A1 1
rs7 rs7 LOC401387 1
rs8 rs8 CDK6 1
rs9 rs9 CDK6 1
rs10 rs10 CDK6 1
")
features<-c("rs5","rs7","rs10")
## calculate
inVar <- toString(shQuote(features, type = "csh")) # 'rs5','rs7','rs10'
fn$sqldf("SELECT * FROM test t
WHERE t.row_names IN ($inVar)"
, row.names = TRUE)
## result
# snp gene distance
#rs5 rs5 KRIT1 1
#rs7 rs7 LOC401387 1
#rs10 rs10 CDK6 1
此外,如果数据足够大,我们可以使用索引来加快速度。有关此详细信息和其他详细信息,请参阅。数据。表解决方案:
library(data.table)
dbsnp <- structure(list(snp = c("rs5", "rs6", "rs7", "rs8", "rs9", "rs10"
), gene = c("KRIT1", "CYP51A1", "LOC401387", "CDK6", "CDK6",
"CDK6"), distance = c(1L, 1L, 1L, 1L, 1L, 1L)), .Names = c("snp",
"gene", "distance"), class = "data.frame", row.names = c("rs5",
"rs6", "rs7", "rs8", "rs9", "rs10"))
DT <- data.table(dbsnp, key='snp')
features <- c('rs5', 'rs7', 'rs9')
DT[features]
snp gene distance
1: rs5 KRIT1 1
2: rs7 LOC401387 1
3: rs9 CDK6 1
库(data.table)
dbsnp检查data.table
包。您可以使用键来执行此操作。您的“行名称”是否与snp列相同?是的,两者相同。我将查看data.table.只是出于兴趣,有没有人知道如果您首先使用foo之类的机制获取行号,是否会有时间差?我尝试按照您建议的方式选择行,这将“通常”完成。它的速度快得多(我没意识到你可以从列表到列表的百分比)。从你显示的内容来看,我认为这两个对象都是“原子向量”,而不是R“列表”。我承认我对它的速度感到有点惊讶。酷-下次我会记住这个区别。事实上,我刚刚从你的帖子中了解到了两者的区别:
library(data.table)
dbsnp <- structure(list(snp = c("rs5", "rs6", "rs7", "rs8", "rs9", "rs10"
), gene = c("KRIT1", "CYP51A1", "LOC401387", "CDK6", "CDK6",
"CDK6"), distance = c(1L, 1L, 1L, 1L, 1L, 1L)), .Names = c("snp",
"gene", "distance"), class = "data.frame", row.names = c("rs5",
"rs6", "rs7", "rs8", "rs9", "rs10"))
DT <- data.table(dbsnp, key='snp')
features <- c('rs5', 'rs7', 'rs9')
DT[features]
snp gene distance
1: rs5 KRIT1 1
2: rs7 LOC401387 1
3: rs9 CDK6 1