reduce-data.frame-method: Reduce a data.frame
In MSnbase: Base Functions and Classes for Mass Spectrometry and Proteomics

Description Usage Arguments Details Value Author(s) Examples

Reduce a data.frame so that the (primary) key column contains only unique entries and other columns pertaining to that entry are combined into semicolon-separated values into a single row/observation.

1 2	## S4 method for signature 'data.frame' reduce(x, key, sep = ";")

`x`	A `data.frame`.
`key`	The column name (currenly only one is supported) to be used as primary key.
`sep`	The separator. Default is `;`.

An important side-effect of reducing a 'data.frame' is that all columns other than the key are converted to characters when they are collapsed to a semi-column separated value (even if only one value is present) as soon as one observation of transformed.

A reduced data.frame.

Laurent Gatto

dfr <- data.frame(A = c(1, 1, 2),
                  B = c("x", "x", "z"),
                  C = LETTERS[1:3])
dfr
dfr2 <- reduce(dfr, key = "A")
dfr2
## column A used as key is still num
str(dfr2)
dfr3 <- reduce(dfr, key = "B")
dfr3
## A is converted to chr; B remains factor
str(dfr3)
dfr4 <- data.frame(A = 1:3,
                   B = LETTERS[1:3],
                   C = c(TRUE, FALSE, NA))
## No effect of reducing, column classes are maintained
str(reduce(dfr4, key = "B"))

Loading required package: BiocGenerics
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    order, paste, pmax, pmax.int, pmin, pmin.int, Position, rank,
    rbind, Reduce, rownames, sapply, setdiff, sort, table, tapply,
    union, unique, unsplit, which.max, which.min

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This is MSnbase version 2.16.0 
  Visit https://lgatto.github.io/MSnbase/ to get started.


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  A B C
1 1 x A
2 1 x B
3 2 z C
  A   B   C
1 1 x;x A;B
2 2   z   C
'data.frame':	2 obs. of  3 variables:
 $ A: num  1 2
 $ B: chr  "x;x" "z"
 $ C: chr  "A;B" "C"
    A B   C
1 1;1 x A;B
2   2 z   C
'data.frame':	2 obs. of  3 variables:
 $ A: chr  "1;1" "2"
 $ B: chr  "x" "z"
 $ C: chr  "A;B" "C"
'data.frame':	3 obs. of  3 variables:
 $ A: int  1 2 3
 $ B: chr  "A" "B" "C"
 $ C: logi  TRUE FALSE NA