Hi there,
I have two questions on matrix manipulation. For the first one, I
want to calculate the product of each column of a matrix (say A) with
another vector (say b). That is, if A has 5 columns (a1, a2, a3, a4,
a5), I want to obtain a matrix with columns (a1*b, a2*b, aA3*b, a4*b,
a5*b). Can I do it directly, without using "for" loop?
For the second one, I have a matrix A of dimension 2 by n (say
columns of a1, a2, ..., an), another matrix B of dimension 2 by 2. I
want to obtain the vector with elements (t(a1) %*% B %*% a1, t(a2)
%*% B %*% a2, ..., t(an) %*% B %*% an). Can I do it without using "for" loop?
Thanks a lot!
Lei Liu
Associate Professor
Division of Biostatistics
Department of Public Health Sciences
University of Virginia School of Medicine
http://people.virginia.edu/~ll9f/
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