# Theta transposes to x

$$h(x) = \sum_{i = 0}^n \theta_i x_i = \theta^T x$$

I understand the above equation apart from the last bit on the right side. I think you have to read it Theta transposes to X. What does it mean? Does someone maybe have an example how it is used? Since I'm not an English native speaker, can you write out, how I would speak it correctly when I read the last part of the equation?

You should read it as "(the transpose of $\theta$) times $x$", or, in this particular case, as "the scalar product of $\theta$ and $x$".
• Remark: $\theta$ is $n\times 1$, so $\theta^T$ is $1\times n$. Now $x$ is $n\times 1$, so $\theta^Tx$ is a product of a $1\times n$ matrix and a $n\times 1$ matrix, i.e. a $1\times1$ matrix, or a scalar. – user1551 Aug 28 '11 at 0:46