KB013. BullScript for Beginners. Trade your own way. Introduction. Preamble

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1 KB013 Trade your own way BullScript for Beginners This is a very basic introduction to the BullCharts scripting language, intended for beginners and novices. It explains key elements of BullScript in very basic terms. More information about BullScript can be found in the BullScript help document which is also available in BullCharts under the Help menu item. Introduction BullScript is already used in the BullCharts software to define chart indicators, and BullCharts scans. For most users most of the time, there is no need to look at the underlying script because the menu options and the drop-down selections enable users to adjust the chart indicator parameters and the scan criteria details for the majority of requirements. However, there can be times when a BullCharts user might want to tweak the underlying BullScript code, or perhaps even write their own code. In the example shown and explained below, we look at using BullScript in a chart indicator, and in particular for the Moving Average chart indicator. Preamble The following discussion explains how BullCharts handles the security price data. There are a number of price variables including the following three which are included within the sample BullScript discussed on the following pages: high low close The price variable high, for example, represents the high price for all bars across the price chart. In addition to these three price variables there are several others open, trades, volume, value. Five of these price variables can be abbreviated to just the first letter, and they can be upper or lower case: High or H Low or L Close or C Open or O Volume or V Value (no abbreviation) Trades (no abbreviation) 1

In the price chart shown below, understand that each high price on the chart for this security (in this case for BHP) is stored within the price variable called high.

2 In the price chart shown below, understand that each high price on the chart for this security (in this case for BHP) is stored within the price variable called high. That is, it is a one-dimension array (or simple table) containing a list of all the price high values. In fact, for the period shown on the chart here from 10 to 25 January, the high values are: $37.72, $37.20, $36.64, $36.7, $36.4, $36.65, $36.72, $36.54, $36.85, $37.15, $37.22 and $ Introduction to Variables and Formulae Consider the following sample BullScript statement: TypicalPrice := (high + low + close)/3; The two characters := are known as the assignment operator. A statement like this comprises a function or calculation on the right-hand side of the assignment operator, and it specifies that the result of this function or calculation is to be stored in the variable named on the left hand side (a typical computer programming standard). In this example TypicalPrice is a variable name which will store the answer to the calculation from the right-hand side. This calculation is simply the addition of three price variables (the high, low and close), with the result divided by three to simply give the average of the three values. It is important to understand that because each of the three price variables actually contains a list of values, then the resulting answer will be a list of values. 2

3 Plotting a basic Moving Average Consider the following sample BullScript statement: MA(C,28,SIMPLE); The simple statement shown here is the Moving Average indicator function (one of many indicator functions), and when appearing in BullScript like this, followed by the semi-colon character, it will cause the Moving Average indicator to be drawn on the price chart. The elements of this sample statement are: MA specifies the function (the Moving Average indicator function) C based on the Close price, 28 a 28 period Moving Average, SIMPLE a Simple Moving Average, as opposed to Exponential, Weighted, etc. This statement could also be written as: ma(close,28,simple); Sample BullScript The Moving Average indicator The following 7 lines are the complete BullScript code that can be used to prompt the user for input values, and generate the Moving Average indicator on a price chart. Each element of the script is explained in the details on the following pages [description="average of price (or other value) calculated over a period of time..."] [target=price; category=moving Average] expr := expression("expression"); method := inputma("method",simple); n := input("time periods",14,1); res := ma(expr,n,method); res; Sample BullScript Line 1 Attribute: Description [description="average of price (or other value) calculated over a period of time..."] The pair of square brackets: [ ] indicates one or more attributes. In this case the attribute called description. The text that follows within the quotation marks can be used elsewhere. 3

Sample BullScript Line 2 Attributes [target=price; category=moving Average] As for line 1 above, the pair of square brackets indicates one (or more) attributes.

4 Sample BullScript Line 2 Attributes [target=price; category=moving Average] As for line 1 above, the pair of square brackets indicates one (or more) attributes. In this case, the two attributes: target, and category, which both have special meaning. The target attribute specifies where the MA curve will be drawn in this case on the Price plot (as opposed to the other possible targets of: Volume, New Pane, etc.). The category attribute literally specifies the category for this item. For the MA, this means that when you use the BullCharts menu option Insert > Indicator to insert an indicator, the resulting dialogue box (see Figure 1 below) has a drop-down labelled Category and will show several indicators of the category Moving Average within the list of items. That is, you can use the category attribute in BullScript to create your own indicator category to assist with finding the indicator at a late time. Figure 1: The "Insert Indicator" dialogue box Category selection. Because both lines 1 and 2 contain attributes, they could be combined in the BullScript into just one statement as follows, noting that the semi-colon character ; is used to separate them. [description="average of price (or other value) calculated over a period of time..."; target=price; category=moving Average] 4

Sample BullScript Line 3 Prompting for input expr := expression("expression"); The BullCharts menu Insert > Indicator dialogue (as shown in Figure 2 below) prompts for three things:- Expression,

5 Sample BullScript Line 3 Prompting for input expr := expression("expression"); The BullCharts menu Insert > Indicator dialogue (as shown in Figure 2 below) prompts for three things:- Expression, Method, and Time Periods. The line 3 prompts for a value for Expression, and stores the entered value in a variable named expr. This will be one of:- Open, High, Low, Close, Volume, Value or Trades (these are known in BullCharts as price variables). Here is a possible variation of this particular statement: price-parameter := expression( Select the price parameter ) The Line 3 above could just as easily have been something like that shown at left where price-parameter is the name of the variable that will store the answer, and Select the price parameter is the text that would be displayed in the Insert > Indicator dialogue box. Figure 2: The "Insert Indicator" dialogue box to enter parameters. Sample BullScript Line 4 Prompting for type of MA method := inputma("method",simple); The keyword here inputma specifically prompts for the type of moving average to be entered (ie. simple, exponential, etc.). The word Method is displayed in the dialogue box prompt (see the Figure above), and SIMPLE is the default value that is offered for the type of MA (note that the text included here as the default must be a valid item from the list of available items). The actual value that is entered or selected is stored for later use in the variable named method. 5

6 Sample BullScript Line 5 Prompting for number of MA periods n := input("time periods",14,1); The keyword here input prompts for a numeric value to be entered for the number of time periods for the Moving Average. The text Time periods is displayed in the dialogue box prompt (see the Figure above), and the two numbers here are: 14 this is the default value offered, and 1 this is the minimum value. The actual value that is entered or selected is stored for later use in the variable named n. Sample BullScript Line 6 The result to be plotted res := ma(expr,n,method); The text: ma(expr,n,method) is the moving average indicator function, and specifies that the Moving Average values are to be calculated for the current security, using the values stored in the three variables that were input above:- expr,n,method. The resulting moving average values are stored in a variable named res. Sample BullScript Line 7 Draw the chart res; This simple statement has the name of a variable, in this case res, followed by a semi-colon. This causes whatever has been specified in the variable res to be drawn on the price chart, remembering that is will be a series of values, and not just one number. Recap A key point to remember is that for any one particular security, all of the seven price variables (ie. Open, High, Low, Close, Volume, Value, Trades) are stored in seven separate one-dimension arrays (an array is basically a table). So when a price variable such as high is stated in a formula or calculation, it is referring to all of the high values for one stock. So when a calculation is performed, the result shown on the left side of the assignment operator := refers to a number of values. If the price varible high contains 100 values for successive high values, then the result will contain 100 values. 6

Introduction. What is BullScript? This BullScript Primer. More BullScript Help

Introduction. What is BullScript? This BullScript Primer. More BullScript Help A BullScript Primer To help BullCharts users understand and learn about the BullScript language, functions, keywords, etc. Document status Fourth draft 19 August 2016 This document is an early draft of