Essentially the same code but one is giving me errors

[kaywai]

Hi,

I have 2 indicators where the difference is one has a List<T> and the other doesn't. The list has tags added to it and nothing else but it is giving out an error message:-

Error on calling 'OnBarUpdate' method on bar 14: You are accessing an index with a value that is invalid since it is out-of-range. I.E. accessing a series [barsAgo] with a value of 5 when there are only 4 bars on the chart.

The one without the list doesn't have any error messages. Can you please tell me what is wrong?

The code below uses the List<T>:-

if (CurrentBar < (level*2 + 10)) return;

// if( DemandLineCount == DemandLineMaxCount )
// {
// DemandLines.RemoveAt(DemandLines.Count-1);
// }

// Identify the first pivot low
if((Math.Min(Low[1],Close[2]) < Math.Min(Low[0],Close[1])) && (Math.Min(Low[1],Close[2]) < Math.Min(Low[2], Close[3])))
{
DemandPoint0 = Math.Min(Low[1],Close[2]);
DemandPoint0Y = CurrentBar-level;
// Draw.Dot(this, "DPDot"+CurrentBar, true, 1, DemandPoint0, Brushes.Red, true);
// Print(Time[0].ToString());
// Print("CurrentBara = " + CurrentBar.ToString());
}
// Hunting for a lower pivot low that has already occurred which meets the same pivot low condition and to draw a ray connecting the 2 points
for( int x = 1; x <= Math.Min(CurrentBar-4, 50); x++)
{
if ((Math.Min(Low[x], Close[x+1]) < Math.Min(Low[x-1], Close[x])) && (Math.Min(Low[x], Close[x+1]) < Math.Min(Low[x+1], Close[x+2])))
{
if (Math.Min(Low[x], Close[x+1]) < DemandPoint0)
{
DemandPoint1 = Math.Min(Low[x], Close[x+1]);
DemandPoint1Y = x;
string drawTag = "DPL" + CurrentBar;
Draw.Ray(this, drawTag, true, DemandPoint1Y, DemandPoint1, CurrentBar - DemandPoint0Y , DemandPoint0, Brushes.Pink, DashStyleHelper.Solid, 1);
DemandLineCount++;
DemandLines.Add(drawTag);
Print(Time[0].ToString());
Print("DemandLines Last Item = "+ DemandLines[DemandLines.Count-1]);
Print("DemandLines Last Item = "+ DemandLines[DemandLines.Count-2]);
// Print("x =" + x.ToString());
// Print("low[x] = " + Low[x].ToString());
// Print("low[1] = " + Low[1].ToString());
// Print("CurrentBar = " + CurrentBar.ToString());
// Print("DemandPoint0 = " + DemandPoint0.ToString());
// Print("DemandPoint0Y = " + DemandPoint0Y.ToString());
break;
}
}
}

The one below does not have List<T>:-

if (CurrentBar < (level*2 + 10)) return;

// Identify the first pivot low
if((Math.Min(Low[1],Close[2]) < Math.Min(Low[0],Close[1])) && (Math.Min(Low[1],Close[2]) < Math.Min(Low[2], Close[3])))
{
DemandPoint0 = Math.Min(Low[1],Close[2]);
DemandPoint0Y = CurrentBar-level;
// Draw.Dot(this, "DPDot"+CurrentBar, true, 1, DemandPoint0, Brushes.Red, true);
// Print(Time[0].ToString());
// Print("CurrentBara = " + CurrentBar.ToString());
}
// Hunting for a lower pivot low that has already occurred which meets the same pivot low condition and to draw a ray connecting the 2 points
for( int x = 1; x <= Math.Min(CurrentBar-4, 50); x++)
{
if ((Math.Min(Low[x], Close[x+1]) < Math.Min(Low[x-1], Close[x])) && (Math.Min(Low[x], Close[x+1]) < Math.Min(Low[x+1], Close[x+2])))
{
if (Math.Min(Low[x], Close[x+1]) < DemandPoint0)
{
DemandPoint1 = Math.Min(Low[x], Close[x+1]);
DemandPoint1Y = x;
Draw.Ray(this, "DPL1"+CurrentBar, true, DemandPoint1Y, DemandPoint1, CurrentBar - DemandPoint0Y , DemandPoint0, Brushes.Pink, DashStyleHelper.Solid, 1);

// Print(Time[0].ToString());
// Print("x =" + x.ToString());
// Print("low[x] = " + Low[x].ToString());
// Print("low[1] = " + Low[1].ToString());
// Print("CurrentBar = " + CurrentBar.ToString());
// Print("DemandPoint0 = " + DemandPoint0.ToString());
// Print("DemandPoint0Y = " + DemandPoint0Y.ToString());
break;
}
}
}

[kaywai]

Hi,

Resolved the issue. It was this line that caused the error:-

Print("DemandLines Last Item = "+ DemandLines[DemandLines.Count-2]);

Why would a print statement cause an error?

Regards
Kay Wai

[kaywai]

Another question I have is when I print out the last item on the DemandLines List (referring to this print statement:

Print("DemandLines Last Item = "+ DemandLines[DemandLines.Count-1])

the first print refers to is when the ray + tag was first drawn and created, which is correct. But I'm getting tags on the following bar (actually for 6 following bars) when there is no new ray being drawn.

Is there something that I'm doing wrong?

[kaywai]

I tried doing away with the "list" after I found some code NinjaTrader PaulH shared regarding a similar matter. Please see attached.

I'm getting the same issue as I described with the list way of doing things. Once it starts printing, the count doesn't stop. I couldn't remove any tag. Below is how I've changed it:-

if (CurrentBar < (level*2 + 10)) return;

// if( DemandLineCount == DemandLineMaxCount )
// {
// DemandLines.RemoveAt(DemandLines.Count-1);
// }

// Identify the first pivot low
if((Math.Min(Low[1],Close[2]) < Math.Min(Low[0],Close[1])) && (Math.Min(Low[1],Close[2]) < Math.Min(Low[2], Close[3])))
{
DemandPoint0 = Math.Min(Low[1],Close[2]);
DemandPoint0Y = CurrentBar-level;
// Draw.Dot(this, "DPDot"+CurrentBar, true, 1, DemandPoint0, Brushes.Red, true);
// Print(Time[0].ToString());
// Print("CurrentBara = " + CurrentBar.ToString());
}
// Hunting for a lower pivot low that has already occurred which meets the same pivot low condition and to draw a ray connecting the 2 points
for( int x = 1; x <= Math.Min(CurrentBar-14, 50); x++)
{
if ((Math.Min(Low[x], Close[x+1]) < Math.Min(Low[x-1], Close[x])) && (Math.Min(Low[x], Close[x+1]) < Math.Min(Low[x+1], Close[x+2])))
{
if (Math.Min(Low[x], Close[x+1]) < DemandPoint0)
{
DemandPoint1 = Math.Min(Low[x], Close[x+1]);
DemandPoint1Y = x;
DemandLineCount++;
// string drawTag = "DPL" + DemandLineCount;
Draw.Ray(this, "DPL" + DemandLineCount, true, DemandPoint1Y, DemandPoint1, CurrentBar - DemandPoint0Y , DemandPoint0, Brushes.Pink, DashStyleHelper.Solid, 1);
// DemandLines.Add(drawTag);
Print(Time[0].ToString());
Print("DemandLine Count is: " + DemandLineCount.ToString());
// Print("DemandLines Last Item = "+ DemandLines[DemandLines.Count-1]);
// Print("DemandLines Last Item = "+ DemandLines[DemandLines.Count-2]);
// Print("x =" + x.ToString());
// Print("low[x] = " + Low[x].ToString());
// Print("low[1] = " + Low[1].ToString());
// Print("CurrentBar = " + CurrentBar.ToString());
// Print("DemandPoint0 = " + DemandPoint0.ToString());
// Print("DemandPoint0Y = " + DemandPoint0Y.ToString());
break;
// To Remove Draw Objects
if( DemandLineCount > DemandLineMaxCount)
{
for( int i = 1; i <= 5; i++)
{
RemoveDrawObject("DPL" + i);
}
DemandLineCount = DemandLineCount - 5;
}
}
}
}

Can somebody please help?

Regards
Kay Wai

[bltdavid]

Resolved the issue. It was this line that caused the error:-

Print("DemandLines Last Item = "+ DemandLines[DemandLines.Count-2]);

Why would a print statement cause an error?

Your thinking is misguided, the syntax of your print statement is fine.

What you have is a logic error, which is more subtle.

The problem is accessing an element in DemandLines that doesn't exist.

Consider this:
On the first time through, when an element is added to DemandLines
for the first time using Add(), the value of DemandLines.Count is 1.

So, that means DemandLines.Count-2 is actually -1, and accessing
the -1 element is what produces the error you see. Negative indexes
are considered illegal in C#.

The way to fix this is to add guard code, to protect against negative
indexes, like this,

if (DemandLines.Count-2 >= 0)
Print("DemandLines Last Item = "+ DemandLines[DemandLines.Count-2]);

Or, since this is a just a print statement, and doesn't really contribute
to the functionality of the code, just delete it.

[kaywai]

bltdavid i did the latter. thx. and your explanation made sense. appreciate it.

i'm having trouble removing draw objects. the second methods is not doing what i thought it would do, So i've gone back to list. But I don't know how to removedrawobject using list.

I'm trying to cap the number of rays drawn to 10 (DemandLineMaxCount) and if it gets to 10, to remove the oldest ray.

the error i'm getting so far in the code below is "cannot convert type 'char' to 'string'. This is the part which is causing the issue.

foreach (string drawTag in DemandLines[DemandLines.Count-1])
{
Print(Time[0].ToString());
Print( drawTag);
if(DemandLines.Count == DemandLineMaxCount )
{
DemandLines.RemoveAt(DemandLines.Count-1);
RemoveDrawObject(drawTag);
}
}

would you mind taking a look?

regards
kaywai

[NinjaTrader_ChelseaB]

Hello kaywai,

bltdavid is right on the money. Can't ask for something that doesn't exit. And negative indexes do not exist. Any index used must be equal to or greater than 0 and less than the size of the collection (count).

https://ninjatrader.com/support/forum/forum/ninjatrader-8/indicator-development/1046200-indicator-that-calculate-in-different-chartime?p=1048513#post1048513

However, where is the code where the list DemandLines is being declared? Is this a List<string>? Or is this a List<char>? Or is this a List<DrawObject> or List<Line>?

What object type is being supplied here as drawTag?

[kaywai]

Hi ChelseaB,

It's a List<string>. I've included the whole code here:-

Need help with this - NinjaTrader Support Forum

I think I've close to being done now save for 1 piece of logic that I have yet to comprehend. Hopefully you can point me in the right direction.

Regards
Kay Wai

[NinjaTrader_ChelseaB]

Hello Kay Wai,

A list of what? A list requries an object type. What is the object type?

Are you creating duplicate forum threads on the same subject? Please let me know so that I merge these threads together if they are duplicates.
Please refrain from making duplicate posts on the forums.

[kaywai]

Hi ChelseaB,

Same indicator but different set of issues. Didn't want to confuse readers. If you think they are the same, feel free to merge them.

Regards
Kay Wai

[NinjaTrader_ChelseaB]

Hello Kay Wai,

If its not the same inquiry make a new thread. If its the same inquiry, (doesn't matter what script), please do not duplicate inquiry.

Is this the same inquiry?

[kaywai]

No it isn't

[NinjaTrader_ChelseaB]

Hello kaywai,

If the object is a string, I would not expect this error that the object is a char type.

May I have you create a new test script so I may test on my end?
Copy just the definition for the List<string>, the instantiation and assignment, and the loop.
Please do not include any other code.

To export a NinjaTrader 8 NinjaScript so this can be shared and imported by the recipient do the following:

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2. Click the 'add' link -> check the box(es) for the script(s) and reference(s) you want to include
3. Click the 'Export' button
4. Enter a unique name for the file in the value for 'File name:'
5. Choose a save location -> click Save
6. Click OK to clear the export location message

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Below is a link to the help guide on Exporting NinjaScripts.
http://ninjatrader.com/support/helpG...-us/export.htm

Once exported, please attach the file as an attachment to your reply.

[kaywai]

Hi Chelsea, what do you mean by instantiation and assignment?

I modified the foreach loop from "foreach (string drawTag in DemandLines[DemandLines.Count-1])" to "foreach (string drawTag in DemandLines.ToList())"

Regards
Kay Wai

[NinjaTrader_ChelseaB]

Hello Kay Wai,

private List<string> myStringList; <-- definition of the variable

new List<string>(); <-- instantiation of the actual object

myStringList = new List<string>(); <-- assigning the instantiated object to a variable