0.5 0.0 0.0 0.0 0.5 0.0 0.0 0.0 0.52 4 6 0 -12 -8 4 0 4= (0.5)I2 4 6 0 -12 -8 4 0 4=

0.52 4 6 0 -12 -8 4 0 4= 1 2 3 0 -6 -4 2 0 2

The diagonal matrix (a**I**) is sometimes
useful in computer graphics.
Say for example that what you want to compute is:

aAx

where a is a scalar and **x** is a column matrix.
Sometimes it is convenient to think of this as:

(aI)Ax

Now every operation is matrix multiplication. This is an advantage since matrix multiplication can be done by graphics hardware.