how to pass a study paramter to a builtin study?

[bpschoch]

I am using the DonchianStudy builtin to get highest high and lowest low of the past N bars (I assume this is the only way to do it). I want to pass in N (the lookback period) from a parameter to my indicator. Normally you initialize the builtin as a global variable passing in the paramters to the builtin. The main function is the one that gets my indicator parameters so how to I pass it to the builtin.

[gspiker]

Hi,

Good question. There are good ways and bad ways of doing this.
The way I would recommend look like:

var study = null;

function PreMain() {
<stuff goes here>
}

function main(nLookback) {

if (study == null)
   study = new DonchianStudy(nLookback);

function PreMain() {
<stuff goes here>
}

function main(nLookback) {

if (nLookback == null)
   nLookback = 20; // Default

if (study == null)
   study = new DonchianStudy(nLookback);

<stuff goes here>
}


If you would like you could even make it so the number can be dynamic:

var study = null;
var nMyLookBack = 20; // Default
var nMyLastLook = 20;

function PreMain() {
<stuff goes here>
}

function main(nLookback) {

if (nLookBack == null){
   nMyLookBack = 20;
   nMyLastLook = nMyLookBack;
}

if (study == null || nMyLastLook != nMyLookBack){
   study = new DonchianStudy(nMyLookback);
   nMyLastLook = nMyLookBack;
}

<stuff goes here>

if (nMyCycle > nMyLookBack)
   nMyLookBack = nMyCycle;
} 

[bpschoch]

ok thanks