# multicolumn in array environment

I want to create a matrix like the following in a math environment but i keep getting compile errors.

\begin{array}{c c c c}
\multicolumn{3}{c}{R} & P \\
0 & 0 & 0 & 1
\end{array}

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It works perfectly with me. Please, provide a full Minimal (non-)Working Example. –  yo' Sep 8 '12 at 22:51
Could you be a bit more specific about the compile error message(s) you're getting? (You're missing \\ at the end of the second array line, but I assume that's not the error you're most concerned with.) Please also indicate the document class you're using, and whether you're using packages such as array that affect the properties of the array environment. –  Mico Sep 8 '12 at 22:56
Perhaps you haven't entered mathmode using either $...$ or $...$ –  cmhughes Sep 9 '12 at 0:54

\documentclass{article}
$\begin{array}{c c c c} \multicolumn{3}{c}{R} & P \\ 0 & 0 & 0 & 1 \end{array}$