array2DF {base}

R Documentation

Convert array to data frame

Description

array2DF converts an array, including list arrays commonly returned by tapply, into data frames for use in further analysis or plotting functions.

Usage

array2DF(x, responseName = "Value",
         sep = "", base = list(LETTERS),
         simplify = TRUE, allowLong = TRUE)

Arguments

x	an array object.
responseName	character string, used for creating column name(s) in the result, if required.
sep	character string, used as separator when creating new names, if required.
base	character vector, giving an initial set of names to create dimnames of x, if missing.
simplify	logical, whether to attempt simplification of the result.
allowLong	logical, specifying whether a long format data frame should be returned if x is a list array and all elements of x are unnamed atomic vectors. Ignored unless simplify = TRUE.

Details

The main use of array2DF is to convert an array, as typically returned by tapply, into a data frame.

When simplify = FALSE, this is similar to as.data.frame.table, except that it works for list arrays as well as atomic arrays. Specifically, the resulting data frame has one row for each element of the array, with one column for each dimension of the array giving the corresponding dimnames. The contents of the array are placed in a column whose name is given by the responseName argument. The mode of this column is the same as that of x, usually an atomic vector or a list.

If x does not have dimnames, they are automatically created using base and sep.

In the default case, when simplify = TRUE, some common cases are handled specially.

If all components of x are data frames with identical column names (with possibly different numbers of rows), they are rbind-ed to form the response. The additional columns giving dimnames are repeated according to the number of rows, and responseName is ignored in this case.

If all components of x are unnamed atomic vectors and allowLong = TRUE, each component is treated as a single-column data frame with column name given by responseName, and processed as above.

In all other cases, an attempt to simplify is made by simplify2array. If this results in multiple unnamed columns, names are constructed using responseName and sep.

Value

A data frame with at least length(dim(x)) + 1 columns. The first length(dim(x)) columns each represent one dimension of x and gives the corresponding values of dimnames, which are implicitly created if necessary. The remaining columns contain the contents of x, after attempted simplification if requested.

See Also

tapply, as.data.frame.table, split, aggregate.

Examples

s1 <- with(ToothGrowth,
           tapply(len, list(dose, supp), mean, simplify = TRUE))

s2 <- with(ToothGrowth,
           tapply(len, list(dose, supp), mean, simplify = FALSE))

str(s1) # atomic array
str(s2) # list array

str(array2DF(s1, simplify = FALSE)) # Value column is vector
str(array2DF(s2, simplify = FALSE)) # Value column is list
str(array2DF(s2, simplify = TRUE))  # simplified to vector

### The remaining examples use the default 'simplify = TRUE' 

## List array with list components: columns are lists (no simplification)

with(ToothGrowth,
     tapply(len, list(dose, supp),
     function(x) t.test(x)[c("p.value", "alternative")])) |>
  array2DF() |> str()

## List array with data frame components: columns are atomic (simplified)

with(ToothGrowth,
     tapply(len, list(dose, supp),
     function(x) with(t.test(x), data.frame(p.value, alternative)))) |>
  array2DF() |> str()

## named vectors

with(ToothGrowth,
     tapply(len, list(dose, supp),
            quantile)) |> array2DF()

## unnamed vectors: long format

with(ToothGrowth,
     tapply(len, list(dose, supp),
            sample, size = 5)) |> array2DF()

## unnamed vectors: wide format

with(ToothGrowth,
     tapply(len, list(dose, supp),
            sample, size = 5)) |> array2DF(allowLong = FALSE)

## unnamed vectors of unequal length

with(ToothGrowth[-1, ],
     tapply(len, list(dose, supp),
            sample, replace = TRUE)) |>
  array2DF(allowLong = FALSE)

## unnamed vectors of unequal length with allowLong = TRUE
## (within-group bootstrap)

with(ToothGrowth[-1, ],
     tapply(len, list(dose, supp), sample, replace = TRUE)) |>
  array2DF() |> str()

## data frame input

tapply(ToothGrowth, ~ dose + supp, FUN = with,
       data.frame(n = length(len), mean = mean(len), sd = sd(len))) |>
  array2DF()

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