Due to over-sized matrix from combn(letters,13), I tried to only output
one selection which is satisfied with the criteria in if clause. This is
how my code looks like and the ERROR message shows:
> li<-combn(letters,13,function(x)(if(apply(( (as.matrix(t(letters%in%
x))) %*% as.matrix(z) )**2,1,sum)==balance){x}else {x=NULL}))
Error in matrix(r, nrow = len.r, ncol = count) :
attempt to set an attribute on NULL
Can anybody know how to solve this problem?
Thanks in advance!
Snow
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