How do I obtain exponential moving averages using the MtGox API? To calculate EMAs, do I need to be recording all of the data coming through MtGox's websocket firehose and manually calculating it myself, or are there static calls I can make to the HTTP API to obtain these figures on demand? How can I obtain an EMA for historical data before I begin recording websocket-streamed data?
Found an answer almost straight away - the answer is to get the data from the BitcoinCharts.com API, rather than MtGox - http://bitcoincharts.com/about/markets-api/

Further info here: Bitcoin Charts API Data