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Subset of one row element based on the column number vector

I have a dataset

data <- cbind(c(1,2,3),c(1,11,21))

I want to extract one element from each row based on the column number given by a vector

selectcol <- c(1,2,2)

In this particular case, the result should be

result

1
11
21

I tried

resul<-apply(data, 1, [,selectcol])

but it doesn't work

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3 answers


You can use col

to match values ​​with selectcol

and a subset data

with it.



data[col(data) == selectcol]
# [1]  1 11 21
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what if you try



 selection <- cbind(1:3, selectcol)
 result <- data[sel]
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This worked for me with the function:

data <- data.frame(cbind(c(1,2,3),c(1,11,21)))

selectcol <- c(1,2,2)

elems<-vector()
extract_elems <- function(data, selectcol) {
  for ( i in 1:length(selectcol)) {
    elems <- append(elems,data[i,selectcol[i]])
  }
  return(elems)
}

output <- extract_elems(data,selectcol)

> output
[1]  1 11 21
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