Communism is clearly Command. The government controls every aspect of the economy.
Libertarianism is Laissez-Faire, where the Government gives full liberty for a free market economy, where people do whatever they want.
Socialism is related with mixed economics, but with government controlling and limiting the economy. It is sort of "You can do whatever you want, as long as you respect the government rules".
I believe Fascism is more related with command. The government decides the trend of the economy, deciding the main focus but giving some liberty for the people close to the government to decide how they are going to do it.