Searching rows in a data frame in R

r

Solution

Edit: The regex way would be:

match.regex <- function(x,data){
  xs <- paste(x,collapse="_")
  dats <- apply(data,1,paste,collapse="_")
  sum(grepl(xs,dats))
}


> match.regex(c(1),dat)
[1] 3
> match.regex(c(0,0,0),dat)
[1] 1
> match.regex(c(1,2),dat)
[1] 2
> match.regex(5,dat)
[1] 0

Surprisingly, this one is faster than other methods given here, and about twice as fast as my solution below, both on small and on big datasets. Regexes got pretty much optimized apparently :

> benchmark(matching(c(1,2),dat),match.regex(c(1,2),dat),replications=1000)
                       test replications elapsed relative 
2 match.regex(c(1, 2), dat)         1000    0.15      1.0 
1    matching(c(1, 2), dat)         1000    0.36      2.4

An approach that gives you the number immediately and works more vectorized, is the following:

matching.row <- function(x,row){
    nx <- length(x)
    sid <- which(x[1]==row)
    any(sapply(sid,function(i) all(row[seq(i,i+nx-1)]==x)))
}

matching <- function(x,data)
  sum(apply(data,1,function(i) matching.row(x,i)),na.rm=TRUE)

Here you first create a matrix with indices that move a window over a row of the same length as the vector you want to match. These windows are then checked against the vector. This approach is followed for every row, and the sum of the rows returning TRUE is what you want.

> matching(c(1),dat)
[1] 3
> matching(c(0,0,0),dat)
[1] 1
> matching(c(1,2),dat)
[1] 2
> matching(5,dat)
[1] 0

Problem

I have strings of numbers not necessarily of the same length e.g. `0,0,1,2,1,0,0,0` `1,1,0,1` `2,1,2,0,1,0` I have imported these into a dataframe in R e.g. the above three strings would give the following three rows (which I shall call `df`): I am looking to write some functions that will help me understand the data. As a starting point - given a numeric vector `x` - I would like a 'process' `P` of establishing the number of rows which contain `x` as a subvector e.g. if `x = c(2,1)` then `P(x) = 2`, if `x = c(0,0,0)` then `P(x) = 1` and if `x = c(1,3)` then `P(x) = 0`. I have many more similar questions though I am hoping I will be able to take the logic from this question and work out some of the other stuff myself.

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