# Undefined control sequence error for equation [duplicate]

I am trying to reproduce the following equation in LaTeX:

nopt(d, B) = argminn {Pt - LMI (d, n, ω + 0.5B) >= Pth }

and the syntax I have used is the following:

$n_{opt}\left(d, B\right) = argmin_n\lbraceP_t - L_{Mi}\left(d, n, \omega + 0.5B\right) \geq P_{th}\rbrace$


This does not compile and I get the

!Undefined Control Sequence Error.

Any suggestions on what I am missing here?

## marked as duplicate by David Carlisle, ChrisS, Martin Schröder, Paul Gessler, JesseJan 27 '15 at 9:59

• Insert a space between \lbrace and P. (The error message you report receiving should indicate which control sequence -- here, \lbraceP -- is undefined. – Mico Jan 27 '15 at 8:49
• It's the same mistake you did here: tex.stackexchange.com/q/224538/27635 – karlkoeller Jan 27 '15 at 9:01

In addition to fixing the erroneous input that's causing LaTeX to report an undefined control sequence error, viz., the lack of a space in \lbraceP -- you should (a) set up argmin as a math operator and (b) render "opt" in upright-roman rather than in math-italic mode. Incidentally, the \left and \right directives don't resize the respective parentheses since the material they enclose isn't large; all they do is to insert unnecessary whitespace and contribute to a "loose" look of the equation. In short, don't use \left and \right here.
\documentclass{article}
$n_{\opt}(d, B) = \argmin_n\bigl\lbrace P_t - L_{Mi}(d, n, \omega + 0.5B) \geq P_{th}\bigr\rbrace$