When I compile the following latex code:
\begin{align}
f_{m}(x) = c_{1,m} \times I(x_{i}^{m} \geqslant t_{m} ) + c_{2,m} \times I(x_{i}^{m} < t_{m} ),
\end{align}
I always get an error:
! Undefined control sequence.
<argument> ..._{1,m} \times I(x_{i}^{m} \geqslant
t_{m} ) + c_{2,m} \times I...
l.124 \end{align}
When I replace \geqslant with >=, it is okay.
I already include the amsmath package. What would cause the problem?
Thanks and regards!
Best Answer
That command isn't defined in the amsmath package, but rather the amssymb package -- put
\usepackage{amssymb}in your preamble and you should be fine.