Fill Disjoint Sets of Values with the Output of a Function

This function splits an object into disjoint sets of values based on a factor, applies a specified function to each set, and returns a new object with the original values replaced by the function's output.

Usage

split_fill(x, fac, FUN)

# S4 method for class 'NeuroVol,factor,function'
split_fill(x, fac, FUN)

Arguments

x

The object to split.

fac

The factor to split by.

FUN

The function used to summarize the sets.

Value

An object of the same class as x, with values replaced by the output of FUN.

Details

The FUN function can either return a scalar for each input vector or a vector equal to the length of the input vector. If it returns a scalar, every voxel in the set will be filled with that value in the output vector.

Examples

## Summarize with mean -- FUN returns a scalar
x <- NeuroSpace(c(10, 10, 10), c(1, 1, 1))
vol <- NeuroVol(rnorm(10 * 10 * 10), x)
fac <- factor(rep(1:10, length.out=1000))
ovol.mean <- split_fill(vol, fac, mean)
identical(dim(ovol.mean), dim(vol))
#> [1] TRUE
length(unique(as.vector(ovol.mean))) == 10
#> [1] TRUE

## Transform by reversing vector -- FUN returns a vector
ovol2 <- split_fill(vol, fac, rev)