HI,
May be this helps:
list1<-lapply(1:5,function(x) data.frame(matrix(sample(1:100,50,replace=TRUE),ncol=5)))
list1<-lapply(list1,function(x) {colnames(x)<-sample(paste0("A",1:50),5,replace=FALSE)
?return(x)})
coldat<-data.frame(col1=c("A9","A35","A7","A30")) #colnames that needs to be extracted
?res<-do.call(cbind,lapply(list1,function(x) x[colnames(x)%in% coldat[,1]]))
?res
#?? A9 A35 A7 A30? A9? A7
#1? 42? 56 10? 67? 14?? 3
#2? 98? 42 49? 38?? 6? 97
#3?? 7? 67 10? 15? 15? 80
#4? 85? 82 24? 97?? 2? 95
#5? 64?? 8 49? 77? 17?? 9
#6? 57? 60? 4? 39?? 4? 89
#7? 86? 41 90? 50? 80? 61
#8? 70? 84 23? 46? 32? 61
#9? 11? 29 42? 76 100 100
#10 92? 19 28? 38? 72? 87
In your case, you have 22 files or dataframes.? You can create a list of 22 dataframes and do the same step as above.
list1<-list(A1,A2,A3,....,A22)
A.K.
----- Original Message -----
From: Silvano Cesar da Costa <silvano at uel.br>
To: r-help at r-project.org
Cc:
Sent: Thursday, November 8, 2012 10:50 AM
Subject: [R] Extracting columns
Hi,
I have 22 files (A1, A2, ..., A22) with different number of columns,
totaling 10,000 columns: c1, c2, c3, ..., c10000
I have another file with a list of 100 columns that I need to extract.
These 100 columns are distributed in 22 files.
How to extract the 100 columns of the 22 files?
I have done it "manually" with the following commands, for example:
cromo1 = read.table ("~ / cromo1.raw ', head = T)
c1 = subset (cromo1, select = c ('c1', 'c50', 'C750'))
in this case, I know that the columns c1, c50 and C750 are on cromo1.raw.
See who need to apply the commands above 22 times.
Is there a way to schedule these operations?
---------------------------------------------
Silvano Cesar da Costa
Universidade Estadual de Londrina
Centro de Ci?ncias Exatas
Departamento de Estat?stica
Fone: (43) 3371-4346
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