[R] a silly question on index of a matrix

[zhihua li]

Hi netters,

This is probably a silly question,but I can't find the answer after 
searching the R-help archives online. ok, I have a matrix. I know there is 
a "10" somewhere in it. Now I want to
know the index of the element "10" in this matrix. That is, if X[i,j]=10, I 
want to know
i and j. Is there a R function to do this? Just like the "find" function in 
matlab.

Thanks all!