How to I /setblock repeaters facing different directions?

You can set a block to repeater via this command:

/setblock ~ ~ ~ minecraft:unpowered_repeater  

That places a repeater facing north, with a one tick delay. If you want to create a different repeater you have to calculate a datavalue, with this formula:

datavalue = direction + (4 * delay)

Where the delay goes from 0 to 3, and the direction goes like this:

• 0: North
• 1: East
• 2: South
• 3: West

For example, if you want to create a repeater facing east with the least amount of delay you calculate:

datavalue = 1 + (4 * 0) = 1

To then create that repeater execute this command:

/setblock ~ ~ ~ minecraft:unpowered_repeater 1

Minecraft 1.13 and newer versions no longer rely on cryptic numbers to encode things like facing, meaning that you can just do /setblock x y z repeater[facing=east]