Find rows of a matrix that form invertible (linearly independent) combinations.
A matrix, with at least as many rows as columns.
The maximum number of rows to consider.
Given a matrix
A, with number of rows equal to or greater than the number of columns, return the combinations of row numbers that constitute invertible square matrices. Consider only the first
nmax rows of the original matrix (to save time for large systems).
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## what combinations of the 20 common amino acids have ## a linearly independent stoichiometry with five elements? # the names of the amino acids aanames <- aminoacids("") # their species indices iaa <- suppressMessages(info(aanames)) # the full stoichiometric matrix A <- i2A(iaa) # the invertible combinations icA <- invertible.combs(A) stopifnot(nrow(icA)==6067) # that's a bit less than 40% of all possible combinations nrow(icA) / ncol(combn(20, 5)) # count the occurrences of each amino acid counts <- table(icA) names(counts) <- aminoacids(1) (sc <- sort(counts)) # the two sulfur-containing ones show up most frequently stopifnot(tail(names(sc), 2)==c("C", "M"))
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