An example of the mixing process. The mixing matrix $A$ transforms the two source signals (⁠$s1$ and $s2$⁠) in the $S$ space to (⁠$s1′$ and $s2′$⁠) in the mixture space $X$⁠. The two source signals can be represented by four points (in black color) in the $S$ space. These points are also transformed using the mixing matrix $A$ into different four points (in red color) in the $X$ space. Additionally, the vectors $w1$ and $w2$ are used to extract the source signal $s1$ and $s2$⁠, and they are plotted in dotted red and blue lines, respectively. $w1$ and $w2$ are orthogonal on $s2′$ and $s1′$⁠, respectively. A color version of this figure is available online.