Using vector sign (bar sign over letters)

[Neel]

Hi All,
I am trying to use the vector sign over a letter (say `A').
I am using \={A} for it. But I am getting the following error
messages. I am giving you the entire piece of code I have written in
latex. Please let me know what is wrong. The pdf document produced have
no apparent error though !!!

thanks a lot for any help,
regards,
Neel


\begin{equation}
\boxed{\begin{array}{rcl}
h_{A} &=& \frac{r^t_A}{r^{t-1}_A} \quad \mbox{and}\quad h_{\={A}} =
\frac{1-r^t_A}{1-r^{t-1}_A} \\
g^t(X_1,\cdots,X_V) &=& g^{t-1}(X_1,\cdots,X_V) \cdot h_{A} \quad
\forall X_1,\cdots,X_V \,\, \mbox{and } \,\, x_{vn}\le X_v\le x_{vm} \\

g^t(X_1,\cdots,X_V) &=& g^{t-1}(X_1,\cdots,X_V) \cdot h_{\={A}} \quad
\forall X_1,\cdots,X_V \,\, \mbox{and } \,\, \{X_v > x_{vm}, \mbox{or}
X_v < x_{vn}\} \
\end{array}}
\end{equation}


The errors are :

1. ! please use \mathaccent for accents in math mode

2. ! You can't use `\spacefactor' in math mode.

[Lars Madsen]

you're using a text accent in math mode.

use \overline{...} instead

/daleif

[Morten Høgholm]

Post by Neel
Hi All,
I am trying to use the vector sign over a letter (say `A').
I am using \={A} for it. But I am getting the following error
messages. I am giving you the entire piece of code I have written in
latex. Please let me know what is wrong. The pdf document produced have
no apparent error though !!!
thanks a lot for any help,

[...]

Post by Neel
1. ! please use \mathaccent for accents in math mode
2. ! You can't use `\spacefactor' in math mode.

Lars gave you the answer. But so did LaTeX actually. You snipped part of
the error message which starts out as this:


LaTeX Warning: Command \= invalid in math mode on input line 34.

! Please use \mathaccent for accents in math mode.
\***@accent ***@spacefactor \spacefactor }\accent
#1 #2\egroup
\spacefactor ...
l.34 $\= A
$
? H
I'm changing \accent to \mathaccent here; wish me luck.
(Accents are not the same in formulas as they are in text.)


As you can see, I typed H (for help) on the following command prompt which
may sometimes result in more clues as to what is wrong but I would say
that LaTeX is pretty clear to begin with.