shift_array: Shift array by index

In ravetools: Signal and Image Processing Toolbox for Analyzing Intracranial Electroencephalography Data

Shift array by index

Description

Re-arrange arrays in parallel

Usage

shift_array(x, along_margin, unit_margin, shift_amount)

Arguments

x	array, must have at least matrix
along_margin	which index is to be shifted
unit_margin	which dimension decides shift_amount
shift_amount	shift amount along along_margin

Details

A simple use-case for this function is to think of a matrix where each row is a signal and columns stand for time. The objective is to align (time-lock) each signal according to certain events. For each signal, we want to shift the time points by certain amount.

In this case, the shift amount is defined by shift_amount, whose length equals to number of signals. along_margin=2 as we want to shift time points (column, the second dimension) for each signal. unit_margin=1 because the shift amount is depend on the signal number.

Value

An array with same dimensions as the input x, but with index shifted. The missing elements will be filled with NA.

Examples

# Set ncores = 2 to comply to CRAN policy. Please don't run this line
ravetools_threads(n_threads = 2L)



x <- matrix(1:10, nrow = 2, byrow = TRUE)
z <- shift_array(x, 2, 1, c(1,2))

y <- NA * x
y[1,1:4] = x[1,2:5]
y[2,1:3] = x[2,3:5]

# Check if z ang y are the same
z - y

# array case
# x is Trial x Frequency x Time
x <- array(1:27, c(3,3,3))

# Shift time for each trial, amount is 1, -1, 0
shift_amount <- c(1,-1,0)
z <- shift_array(x, 3, 1, shift_amount)

oldpar <- par(mfrow = c(3, 2), mai = c(0.8, 0.6, 0.4, 0.1))
for( ii in 1:3 ){
  image(t(x[ii, ,]), ylab = 'Frequency', xlab = 'Time',
        main = paste('Trial', ii))
  image(t(z[ii, ,]), ylab = 'Frequency', xlab = 'Time',
        main = paste('Shifted amount:', shift_amount[ii]))
}
par(oldpar)

ravetools documentation built on Sept. 11, 2024, 9:06 p.m.