Referencing historical value of variable or recursive error

[Cyprus2010]

Hi. A beginner coder here, looking for some guidance on a piece of code I'm trying to write.

I'd like to write a function that uses the previous day's value of a variable to calculate today's variable (for several variables). Even though I have 6 or 7 variables, it only needs to look back 1 day so I searched here and found what seems to be the simplest solution which is to declare global variables and then use getBarState() to store the T-1 values (rather than use ref() or some array solution). Here's a snippet of the code I wrote:

function preMain() {
    setStudyTitle("test");
    setCursorLabelName("test", 0);
 
}

    var i1;
    var i1_1;
    var i2;
    var i2_1;

function main(constA, constB) {

    if (constA == null) {
     constA = 10;
}
    if (constB == null) {
     constB = 1;
}
    
    if ( isNull(i1) ) {
    i1 = 0;
}
    if ( isNull(i2) ) {
    i2 = 0;
}
  
    if ( isNull(i1_1) ) {
    i1_1 = 0;
}
    if ( isNull(i2_1) ) {
    i2_1 = 0;
}


    if ( getBarState() == BARSTATE_NEWBAR ) {
        
        i1_1 = i1;
        i2_1 = i2;
        
}

//Const Variables

var c0 = (constA - 1.0) * constB + 1.0;
var c1 = 2 / (c0 + 1.0);
var c2 = 1 + c1;

//Calc
    if ( close(0) > 0 ) {

i1 = c1 * close(0) + c2 * i1_1 ;
i2 = c1 * i1 + c2 * i2_1;

}
        return new Array (i1, i2)

} 

As it stands the function returns nothing on the chart. I have tested it and the function returns values correctly for c0, c1 and c2. It also returns a value if I take out the (i1_1) value in the final calculation of i1. So this led me to believe that either I have the getBarState() function wrong or some kind of null/recursive error in calculating i_1.

Can anyone give some pointers? Also if anyone can suggest a more elegant way of doing the null checks (or for the entire setup of the script for that matter), I would be most grateful. Thank you.

[ACM]

Cyprus2010
Your formula is not returning anything because the null checks for i1, i1_1 etc never return true as those variables are undefined hence they never get assigned a value.
To verify this add the following line
if(getCurrentBarCount()==1) debugPrintln(i1);
immediately before this code in your formula
if ( isNull(i1) ) {
i1 = 0;
}
and you will see that in the Formula Output you get undefined
Now add = null to each global variable declaration ie
var i1 = null;
var i1_1 = null;
var i2 = null;
var i2_1 = null;
and you will see that your formula will return values (whether these are what you ultimately want is a different issue)
Anyhow enclosed below is a simplified version of your formula (it returns the same values as your corrected formula)
Alex

Edit after post: I replaced fP1 with fP2 in the second FunctionParameter

function preMain() {
         setStudyTitle("test");
         setCursorLabelName("test", 0);
    
        var fP1 = new FunctionParameter("constA",FunctionParameter.NUMBER);
        fP1.setName("Constant 1");
        fP1.setDefault(10);

        var fP2 = new FunctionParameter("constB",FunctionParameter.NUMBER);
        fP2.setName("Constant B");
        fP2.setDefault(1);
 }

var i1 = 0;
var i1_1 = 0;
var i2 = 0;
var i2_1 = 0;

function main(constA, constB) {
    
//Const Variables
    var c0 = (constA - 1.0) * constB + 1.0;
    var c1 = 2 / (c0 + 1.0);
    var c2 = 1 + c1;
    
    if ( getBarState() == BARSTATE_NEWBAR ) {
        i1_1 = i1;
        i2_1 = i2;
    }

//Calc
    if ( close(0) > 0 ) {
        i1 = c1 * close(0) + c2 * i1_1 ;
        i2 = c1 * i1 + c2 * i2_1;
    }

    return new Array (i1, i2)
 } 

Hi. A beginner coder here, looking for some guidance on a piece of code I'm trying to write.

I'd like to write a function that uses the previous day's value of a variable to calculate today's variable (for several variables). Even though I have 6 or 7 variables, it only needs to look back 1 day so I searched here and found what seems to be the simplest solution which is to declare global variables and then use getBarState() to store the T-1 values (rather than use ref() or some array solution). Here's a snippet of the code I wrote:

function preMain() {
    setStudyTitle("test");
    setCursorLabelName("test", 0);
 
}

    var i1;
    var i1_1;
    var i2;
    var i2_1;

function main(constA, constB) {

    if (constA == null) {
     constA = 10;
}
    if (constB == null) {
     constB = 1;
}
    
    if ( isNull(i1) ) {
    i1 = 0;
}
    if ( isNull(i2) ) {
    i2 = 0;
}
  
    if ( isNull(i1_1) ) {
    i1_1 = 0;
}
    if ( isNull(i2_1) ) {
    i2_1 = 0;
}


    if ( getBarState() == BARSTATE_NEWBAR ) {
        
        i1_1 = i1;
        i2_1 = i2;
        
}

//Const Variables

var c0 = (constA - 1.0) * constB + 1.0;
var c1 = 2 / (c0 + 1.0);
var c2 = 1 + c1;

//Calc
    if ( close(0) > 0 ) {

i1 = c1 * close(0) + c2 * i1_1 ;
i2 = c1 * i1 + c2 * i2_1;

}
        return new Array (i1, i2)

} 

As it stands the function returns nothing on the chart. I have tested it and the function returns values correctly for c0, c1 and c2. It also returns a value if I take out the (i1_1) value in the final calculation of i1. So this led me to believe that either I have the getBarState() function wrong or some kind of null/recursive error in calculating i_1.

Can anyone give some pointers? Also if anyone can suggest a more elegant way of doing the null checks (or for the entire setup of the script for that matter), I would be most grateful. Thank you.

[Cyprus2010]

Alex. Thanks for the prompt response. I immediately see that I get values on the chart after making the changes you suggested. I will incorporate your ideas into my code and see where it leads me. Thanks again.

[ACM]

Cyprus2010
You are welcome
Alex

Alex. Thanks for the prompt response. I immediately see that I get values on the chart after making the changes you suggested. I will incorporate your ideas into my code and see where it leads me. Thanks again.