Unit Tests for Position/Portfolio - While I've not mentioned it directly in diary entries #1 and #2, I've actually been writing some unit tests for the Portfolio and Position objects. Since these are so crucial to the calculations of the strategy, one must be extremely confident that they perform as expected. An additional benefit of such tests is that they allow the underlying calculation to be modified, such that if all tests still pass, we can be confident that the overall system will continue to behave as expected.

For securities, the definition of margin includes three important concepts: the Margin Loan, the Margin Deposit and the Margin Requirement. The Margin Loan is the amount of money that an investor borrows from his broker to buy securities. The Margin Deposit is the amount of equity contributed by the investor toward the purchase of securities in a margin account. The Margin Requirement is the minimum amount that a customer must deposit and it is commonly expressed as a percent of the current market value. The Margin Deposit can be greater than or equal to the Margin Requirement. We can express this as an equation:


This article will address several questions pertaining to Margin within Forex trading, such as: What is Margin? What is free margin in Forex?' and What is Margin level in Forex? Every broker has differing margin requirements and offers different things to traders, so it's good to understand how this works first, before you choose a broker and begin trading with a margin.

Currency markets are important to a broad range of participants, from banks, brokers, hedge funds and investor traders who trade FX. Any company that operates or has customers overseas will need to trade currency. Central banks can also be active in currency markets, as they seek to keep the currency they are responsible for trading within a specific range.
Margin calls are mechanisms put in place by your Forex broker in order to keep your used margin secure. Remember, your used margin is allocated by your broker as the collateral for funds borrowed from your broker. A margin call happens when your free margin falls to zero, and all you have left in your trading account is your used, or required margin. When this happens, your broker will automatically close all open positions at current market rates.

GUI Control and Reporting - Right now the system is completely console/command line based. At the very least we will need some basic charting to display backtest results. A more sophisticated system will incorporate summary statistics of trades, strategy-level performance metrics as well as overall portfolio performance. This GUI could be implemented using a cross-platform windowing system such as Qt or Tkinter. It could also be presented using a web-based front-end, utilising a web-framework such as Django.
All currency trading is done in pairs. Unlike the stock market, where you can buy or sell a single stock, you have to buy one currency and sell another currency in the forex market. Next, nearly all currencies are priced out to the fourth decimal point. A pip or percentage in point is the smallest increment of trade. One pip typically equals 1/100 of 1 percent.

In particular I've made the interface for beginning a new backtest a lot simpler by encapsulating a lot of the "boilerplate" code into a new Backtest class. I've also modified the system to be fully workable with multiple currency pairs. In this article I'll describe the new interface and show the usual Moving Average Crossover example on both GBP/USD and EUR/USD.


Borrowing money to purchase securities is known as "buying on margin". When an investor borrows money from his broker to buy a stock, he must open a margin account with his broker, sign a related agreement and abide by the broker's margin requirements. The loan in the account is collateralized by investor's securities and cash. If the value of the stock drops too much, the investor must deposit more cash in his account, or sell a portion of the stock.
In addition, I've had some comments from people suggesting that they'd like to see more varied order types than the simple Market Order. For carrying out proper HFT strategies against OANDA we are going to need to use Limit Orders. This will probably require a reworking of how the system currently executes trades, but it will allow a much bigger universe of trading strategies to be carried out.
Margin is one of the most important concepts of Forex trading. However, a lot of people don't understand its significance, or simply misunderstand the term. A Forex margin is basically a good faith deposit that is needed to maintain open positions. A margin is not a fee or a transaction cost, but instead, a portion of your account equity set aside and assigned as a margin deposit.
To date, we've been experimenting with the OANDA Rest API in order to see how it compared to the API provided by Interactive Brokers. We've also seen how to add in a basic portfolio replication element as the first step towards a proper event-driven backtesting system. I've also had some helpful comments on both previous articles (#1 and #2), which suggests that many of you are keen on changing and extending the code yourselves.
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This material does not contain and should not be construed as containing investment advice, investment recommendations, an offer of or solicitation for any transactions in financial instruments. Please note that such trading analysis is not a reliable indicator for any current or future performance, as circumstances may change over time. Before making any investment decisions, you should seek advice from independent financial advisors to ensure you understand the risks.
Currency markets are important to a broad range of participants, from banks, brokers, hedge funds and investor traders who trade FX. Any company that operates or has customers overseas will need to trade currency. Central banks can also be active in currency markets, as they seek to keep the currency they are responsible for trading within a specific range.
Options involve risk and are not suitable for all investors. For more information read the "Characteristics and Risks of Standardized Options". For a copy call Interactive Brokers' Client Services on 312-542-6901. Before trading, clients must read the relevant risk disclosure statements on our Warnings and Disclosures page - http://www.interactivebrokers.com/disclosures. Trading on margin is only for sophisticated investors with high risk tolerance. You may lose more than your initial investment. For additional information regarding margin loan rates, see http://www.interactivebrokers.com/interest. Security futures involve a high degree of risk and are not suitable for all investors. The amount you may lose may be greater than your initial investment. Before trading security futures, read the Security Futures Risk Disclosure Statement. For a copy visit http://www.interactivebrokers.com/disclosures. Structured products and fixed income products such as bonds are complex products that are more risky and are not suitable for all investors. Before trading, please read the Risk warning and Disclosure Statement at http://www.interactivebrokers.com/disclosures. There is a substantial risk of loss in foreign exchange trading. The settlement date of foreign exchange trades can vary due to time zone differences and bank holidays. When trading across foreign exchange markets, this may necessitate borrowing funds to settle foreign exchange trades. The interest rate on borrowed funds must be considered when computing the cost of trades across multiple markets.
Forex margin is a good faith deposit that a trader puts up as collateral to initiate a trade. Essentially, it is the minimum amount that a trader needs in the trading account to open a new position. This is usually communicated as a percentage of the notional value (trade size) of the forex trade. The difference between the deposit and the full value of the trade is “borrowed” from the broker.
Local Portfolio Handling - In my opinion carrying out a backtest that inflates strategy performance due to unrealistic assumptions is annoying at best and extremely unprofitable at worst! Introducing a local portfolio object that replicates the OANDA calculations means that we can check our internal calculations while carrying out practice trading, which gives us greater confidence when we later use this same portfolio object for backtesting on historical data.
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