R: return array index of partial string match -

suppose have 10x10 matrix populated 1:100. want search numbers ending in '0', , want [i,j] index numbers. tried which(..., arr.ind=t), couldn't find function works it. tried grep('0$', ...) returns single index of matrix vector. suppose possible turn number binary index, there simpler way?

x <- t(matrix(1:100,nrow=10,ncol=10)) #  output: #  [1,]  1  10 #  [2,]  2  10 #  ... #  [10,] 10 10 

we can convert grepl output matrix same dim original 'x' , use which arr.ind=true.

which(`dim<-`(grepl('0$', x), dim(x)), arr.ind=true) #       row col # [1,]   1  10 # [2,]   2  10 # [3,]   3  10 # [4,]   4  10 # [5,]   5  10 # [6,]   6  10 # [7,]   7  10 # [8,]   8  10 # [9,]   9  10 #[10,]  10  10 

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or without changing dim, grepl output logical vector, negate (!) true becomes false , false true, multiply original matrix output in matrix. replace values in 'x' ends '0' 0. negate (!) again 0 gets convert true , others false. use which , index corresponding true values.

which(!x*(!(grepl('0$', x))), arr.ind=true)