Hello, I try reproduce custom algorithm from NMF package tutorial on simple simulation data from the package: n <- 50; r <- 3; p <- 20 V <-syntheticNMF(n, r, p, noise=TRUE) nmf(V, 3, my.algorithm, scale.factor=10) But I get the following error: Error in metagenes(fit(seed)) <- abs(pca$rotation[, 1:factorization.rank]) : could not find function "metagenes<-" What is wrong here? This is the algorithm: my.algorithm <- function(x, seed, scale.factor=1){ # do something with starting point # for example: # 1. compute principal components pca <- prcomp(t(x), retx=TRUE) # 2. use the absolute values of the first PCs for the metagenes # Note: the factorization rank is stored in object 'start' factorization.rank <- nbasis(seed) metagenes(fit(seed)) <- abs(pca$rotation[,1:factorization.rank]) # use the rotated matrix to get the mixture coefficient # use a scaling factor (just to illustrate the use of extra parameters) metaprofiles(fit(seed)) <- t(abs(pca$x[,1:factorization.rank])) / scale.factor # return updated data return(seed) } Thanks! Pavel [[alternative HTML version deleted]]