Draw the graph of x=f(y) on the same axes of y=f(x)

it is very easy.
just you have to do some calculations.

for the first segment, I will do the calculation, for rest you can do.

first segment (-1,2) (1,4)
since the graph is a straight line, equation can be found out as,
y-y1 = (y2-y1/x2-x1)(x-x1)
substituting values, you will get equation as
y - 2 = 2/5(x+1)
just rearrange to look it like f(y) = x
ie x = 5/2(y-2) - 1
now for the
first segment (-1,2) (1,4) just plot this line and you will have your graph for x = f(y)
likewise do it for second segment too
for third segment,
it will remain as y = 1 for the reigon for which it holds, ie from 2,1 to 4,1
for the fouth segment, calculate as I have done above for a straight line

This is so simple equation and very helpful.