Introduction to the MetaStock programming language

MetaStock's programming language breaks down into three simple components:

• Parameters: the raw data, such as open, high, low and close
• Mathematical operators: +, −, /, *
• Functions: a moving average, the Stochastic Oscillator, the RSI...

Combined, these three form the foundation of everything, and they drive MetaStock's four major tools: the Indicator Builder, the Explorer, the Expert Advisor and the System Tester.

The language was patterned after spreadsheet formulas. If you can build a reasonable spreadsheet, you are halfway to reading MetaSpeak already. If you can't, no matter: we begin at the beginning.

Parameters: the price array identifiers

Price array identifiers are the atoms of technical analysis: the open, high, low, close, volume and open interest of each period. In a formula they identify which price field the calculation should operate on.

• Open: the first trade of the period. On daily data the open carries extra meaning: it is the consensus price after everybody has slept on it.
• High: the highest traded price of the period, the point where supply overcame demand. Sellers were willing to sell higher; the high is the most buyers would pay.
• Low: the lowest traded price, the point where demand overcame supply. Buyers were willing to buy lower; the low is the least sellers would accept.
• Close: the last traded price of the period, and thanks to its availability, the most-used value in technical analysis. The relationship between close and open is the day's verdict in miniature.
• Volume: the number of units traded in the period, the fuel gauge behind any move.
• Open interest: for futures, the number of open contracts outstanding.

How they look in a formula

In MetaSpeak the identifiers abbreviate to single letters or short names: O, H, L, C, V (also written OPEN, HIGH and so on). So the simplest useful formula you will ever write:

( H + L ) / 2

...the midpoint of each bar. Already recognisable as spreadsheet thinking: values, combined with operators, producing a new value for every bar on the chart. That pattern, repeated with richer ingredients, is the entire language.

Try it before Lesson 2

Open MetaStock's Indicator Builder (Tools menu), create a new indicator, and plot (H + L)/2 on any chart. Watching your own first formula draw itself is worth ten pages of theory. In Lesson 2 we add the operators properly and start building expressions with real logic in them.