interpolMatrix: Interpolate matrix

In soundgen: Sound Synthesis and Acoustic Analysis

Interpolate matrix

Description

Performs a chosen type of separable interpolation across both rows and columns of a matrix, in effect up- or downsampling a matrix to required dimensions. Rownames and colnames are also interpolated as needed. Make sure there are no NAs in the input to avoid unpredictable behavior (dropped by approx and spline, propagated by resample).

Usage

interpolMatrix(
  m,
  nr = NULL,
  nc = NULL,
  interpol = c("approx", "spline", "resample")
)

Arguments

m	input matrix of numeric values
nr, nc	target dimensions
interpol	interpolation method ('approx' for linear, 'spline' for spline, 'resample' for more nuanced resampling with low-pass filtering). NB: only linear interpolation is implemented for matrices of complex numbers

Examples

m = matrix(1:12 + rnorm(12, 0, .2), nrow = 3)
rownames(m) = 1:3; colnames(m) = 1:4
soundgen:::interpolMatrix(m)  # just returns the original
soundgen:::interpolMatrix(m, nr = 10, nc = 7)
soundgen:::interpolMatrix(m, nr = 10, nc = 7, interpol = 'spline')
soundgen:::interpolMatrix(m, nr = 2, nc = 7)
soundgen:::interpolMatrix(m, nr = 2, nc = 3)

# input matrices can have a single row/column
soundgen:::interpolMatrix(matrix(1:5, nrow = 1), nc = 9)
soundgen:::interpolMatrix(matrix(1:5, ncol = 1), nr = 5, nc = 3)

# use resample() with a low-pass filter to avoid artifacts
a = matrix(c(rep(0, 10), 1, rep(0, 10)))
soundgen:::interpolMatrix(a, nr = 5)  # ok
soundgen:::interpolMatrix(a, nr = 6)  # spike lost
soundgen:::interpolMatrix(a, nr = 6, interpol = 'resample')  # ok

# complex values
cm = matrix(complex(real = 1:9, imaginary = 1:9), nrow = 3)
soundgen:::interpolMatrix(cm, nr = 5)

soundgen documentation built on Sept. 20, 2026, 5:07 p.m.