
Hi, 
I have a (correlation) matrix and I want to select a subset of its cells depending on the combination of their column and row names.  
This illustrates my problem: mtrx <- matrix(c(1,2,3,4,5,6,7,8,9), nrow=3, ncol=3, dimnames = list(c('c132','c432', 'c233'),  c('r132','r233', 'r432')))> mtrx     r132 r233 r432c132    1    4    7c432    2    5    8c233    3    6    9
At this point I want to compute the mean of the cells in which the column and the row names share the same suffix (i.e., the cells mtrx[1,1], mtrx[2,3], mtrx[3,2]). By suffix I mean the last three digits of the row/col name.
I need a generic code (and not vec<-c(mtrx[1,1], mtrx[2,3], mtrx[3,2])) because I don't know in advance how many rows and columns I will have (currently 118). 
Thanks, Yoav 		 	   		  
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