scripts/temp-distance-functions/expand_matrix_list.R

In jtipton25/sgMRA: Multi-Resolution Gaussian Process Approximations with Stochastic Gradient Descent

expand_matrix_list <- function(A_list) {
    M <- length(A_list)
    n <- rep(0, M)
    p <- rep(0, M)

    rows <- vector(mode = 'list', length = M)

    for (m in 1:M) {
        n[m] <- nrow(A_list[[m]])
        p[m] <- ncol(A_list[[m]])
    }
    if (any(n > p)) {
        stop("All matrices in the list must have more columns than rows")
    }


    for (m in 1:M) {

        if (m == 1) {
            C <-  Matrix(0, nrow = n[m], ncol = sum(p[2:M]), sparse = TRUE)
            rows[[m]] <- cbind(A_list[[m]], C)

        } else if (m == M) {
            B <-  Matrix(0, nrow = n[m], ncol = sum(p[1:(M-1)]), sparse = TRUE)
            rows[[m]] <- cbind(B, A_list[[m]])
        } else {
            B <-  Matrix(0, nrow = n[m], ncol = sum(p[1:(m-1)]), sparse = TRUE)
            C <-  Matrix(0, nrow = n[m], ncol = sum(p[(m+1):M]), sparse = TRUE)
            rows[[m]] <- cbind(B, cbind(A_list[[m]], C))
        }
    }
    all_rows <- do.call(rbind, rows)
    A <- expand_matrix(all_rows)
    return(A)
}