Matrix Shear Mapping Transformation

Shear mapping (let $m\approx 1$ for the example):

$$\left(\begin{array}{cc}1& m\\ 0& 1\end{array}\right)\cdot \left(\begin{array}{c}x\\ y\end{array}\right)=\left(\begin{array}{c}x+my\\ y\end{array}\right)$$