Page History: Scripting Overview
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Page Revision: 2011/07/22 16:30
Code Structure
Scripting code consists of one or more statements that are executed by the script interpreter.
Individual statements are separated by semicolons. White spaces (spaces, tabs, carriage returns, etc.) have no effect on how scripts are interpreted. Scripts are case-insensitive (e.g.
sma is the same as
SMA).
Statements can do the following:
- Perform a calculation.
- Assign a value or calculation to a variable name.
- Accept user input into a variable.
- Plot values on a chart in various different formats.
- Configure the chart.
Lets take a look at a script that computes the Disparity Index indicator:
VSCALE_DECIMALS(2);
periods = INPUT("MA Periods", 14, 1, 100);
indcolor = INPUT("Color", Color.Blue);
ma = SMA(CLOSE, periods);
di = 100 * ((CLOSE - ma) / ma);
PLOT_HISTOGRAM(di, 0.75, indcolor);
SUMMARY("Disparity Index({?}) {?:F2}", periods, di);
The first line,
VSCALE_DECIMALS(2);, is a chart configuration command that states that we want numbers on the indicator value scale to display out to two decimal places.
Next, we accept some user input for the number of moving average periods and the color to draw the indicator. These values are stored in variable names (
periods and
indcolor) for later use in the script.
The indicator values are calculated next. This is done in two steps to make it easier to read and also to improve efficiency of the script. A simple moving average of the closing price is first computed and stored in variable
ma. As you can see, we feed the user configurable number periods into the SMA function. This allows for the periods to be adjusted through the chart properties window without having to open and modify the script every time. Finally, we compute the disparity index as a percentage and store it in variable
di. This is simply a computation of the percent difference of the current closing price to the moving average and the syntax was designed to be as intuitive as possible.
The last thing done by the script is to plot the values and display a summary.
This script produces the following output:
Assign Values to Variables
Compute SMA 3 Different Ways
Plot Lines, Histograms, Wavecrests, Bands, Points¶
Plot Limit Lines, Center Lines and Range Markers¶
Display a Customized Summary
Format Tick Prices for Display
Change Plot Colors/Styles on the Fly
Custom Colors and Transparency¶
Accept Input via the Properties Window
Configure the Value Scale for Indicators
Using Aggregation Functions
Using IF Statements
Using the Cross Functions
Using NIL
Perform Recursive Calculations
Don't Reassign Variables
Don't Cause Circular References