linear_access {neuroim2} | R Documentation |
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)
[Package neuroim2 version 0.8.1 Index]