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I have a matrix X1 with 6 columns. Column 3 in this X1 matrix contains RouteNo. I also have a vector V1 which is extracted from another matrix. Few values from this vector matches with RouteNo in X1. The task is to take a subset from matrix X1 where RouteNo from X1 matches with RouteNo from V1. V1 contains extra RouteNo than in matrix X1.
> X1
V1 V2 V3 V4 V5 V6
1 1 2 84072082 1 2000 0
2 2 2 84046006 1 2000 0
3 3 2 84046006 1 2001 0
4 4 2 84046006 1 2002 0
5 5 2 84021002 1 2002 0
6 6 2 84021002 1 2003 0
7 7 2 84021002 1 2003 0
8 8 2 84021002 1 2004 0
9 9 2 84021002 1 2005 0
10 10 2 84021002 1 2005 0
11 11 2 12468015 1 2006 0
12 12 2 12468015 1 2007 0
13 96 2 12468015 2 2000 0
> V1
[1] 84021001 84021002 84021105 84046006 84046007 84046008 84046009 84046011 84046013 84046014
> n2 = subset(X1, subset = X1[,3] %in% V1)
> dim(n2)
[1] 0 6
I tried using subset function but I am not getting the desired result. I expect to get the matrix as below
2 2 2 84046006 1 2000 0
3 3 2 84046006 1 2001 0
4 4 2 84046006 1 2002 0
5 5 2 84021002 1 2002 0
6 6 2 84021002 1 2003 0
7 7 2 84021002 1 2003 0
8 8 2 84021002 1 2004 0
9 9 2 84021002 1 2005 0
Is there any other way to get the result? Any help is appreciated. Thank in advance.
940
You should therefore use a comma to separate the rows you want to select from the columns. For example: my_matrix[1,2] selects the element at the first row and second column. my_matrix[1:3,2:4] results in a matrix with the data on the rows 1, 2, 3 and columns 2, 3, 4.
The way you tell R that you want to select some particular elements (i.e., a 'subset') from a vector is by placing an 'index vector' in square brackets immediately following the name of the vector. For a simple example, try x[1:10] to view the first ten elements of x.
You are running into problems with scoping. You have a column named V1 in your data.frame x1. Change your look up vector to a name that isn't a column name and everything should be fine, i.e.:
subset(x1, V3 %in% v1)
or use [ to index directly
x1[x1$V3 %in% V1,]
The proof is in the pudding:
txt1 <- " V1 V2 V3 V4 V5 V6
1 1 2 84072082 1 2000 0
2 2 2 84046006 1 2000 0
3 3 2 84046006 1 2001 0
4 4 2 84046006 1 2002 0
5 5 2 84021002 1 2002 0
6 6 2 84021002 1 2003 0
7 7 2 84021002 1 2003 0
8 8 2 84021002 1 2004 0
9 9 2 84021002 1 2005 0
10 10 2 84021002 1 2005 0
11 11 2 12468015 1 2006 0
12 12 2 12468015 1 2007 0
13 96 2 12468015 2 2000 0"
txt2 <- "84021001 84021002 84021105 84046006 84046007 84046008 84046009 84046011 84046013 84046014"
x1 <- read.table(textConnection(txt1))
#Note the lowercase
v1 <- read.table(textConnection(txt2))
#Make "V1" as you have it
V1 <- v1
> #Bad
> dim(subset(x1, V3 %in% V1))
[1] 0 6
> #Good
> dim(subset(x1, V3 %in% v1))
[1] 9 6
#Does subset method equal the direct indexing method
> all.equal(subset(x1, V3 %in% v1),x1[x1$V3 %in% V1,])
[1] TRUE
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