linear_access: Extract values from an array-like object using linear...

In bbuchsbaum/neuroim2: Data Structures for Brain Imaging Data

Extract values from an array-like object using linear indexing.

Description

This function extracts the values of the elements in an array-like object using linear indexing. Linear indexing is a way of indexing an array by a single index that is computed from multiple indices using a formula.

Usage

linear_access(x, i, ...)

Arguments

x	a data source.
i	a vector of indices.
...	additional arguments to be passed to methods.

Value

A vector containing the values at the specified linear indices of x.

Examples

# Create a sparse neuroimaging vector
bspace <- NeuroSpace(c(10,10,10,100), c(1,1,1))
mask <- array(rnorm(10*10*10) > .5, c(10,10,10))
mat <- matrix(rnorm(sum(mask)), 100, sum(mask))
svec <- SparseNeuroVec(mat, bspace, mask)

# Extract values using linear indices
# Get values from first timepoint at voxels 1,2,3
indices <- c(1,2,3)
vals <- linear_access(svec, indices)

# Get values from multiple timepoints and voxels
# First voxel at timepoint 1, second voxel at timepoint 2
indices <- c(1, 1000 + 2) # 1000 = prod(10,10,10)
vals <- linear_access(svec, indices)

bbuchsbaum/neuroim2 documentation built on Feb. 26, 2025, 3:49 p.m.