Comparing previous bar

[antonek]

Hi,
I am trying to develop my first indicator and got stuck with simple task -> when the high of the current bar is higher then previous draw an arrow:

protected override void OnBarUpdate() {
      if (High[1]<High[0]) {
		DrawArrowUp("UpArrow" + CurrentBar, false, 0, Low[0] - 1, Color.DarkGreen);
      }
}

But this code does not draw any arrow. On the other hand when I try to compare with the "future" bar it works correctly...

protected override void OnBarUpdate() {
      if (High[0]<High[-1]) {
		DrawArrowUp("UpArrow" + CurrentBar, false, 0, Low[0] - 1, Color.DarkGreen);
      }
}

What am I doing wrong? Thanks

[NinjaTrader_AdamP]

antonek,

I am happy to assist you.

It is not recommended to plot these by checking future values.

What about this setup isn't plotting these correctly? Are they plotting 1 bar too early or something similar?

[antonek]

Thanks for reply.

Of course I don't want to check future values - I tried that code just to verify that the syntax is correct...

So my idea is to check high of current bar with high one bar ago, shouldn't High[1]<High[0] do that? But my indicator doesn't draw any arrow. Enclosed see my indicator.

[NinjaTrader_AdamP]

antonek,

You may want to try :

if (High[1]<High[0])
{
DrawArrowUp("UpArrow" + CurrentBar, false, 0, Low[0] - 1*TickSize, Color.DarkGreen);
}

[antonek]

Unfortunately it didnt help... as you can see in enclosed images no arrow is drawn.

[NinjaTrader_AdamP]

antonek,

One thing I just noticed is that you aren't checking to make sure 2 bars are in the high series. There may be a log message about index out of bounds.

Please add the following to the beginning of your OnBarUpdate() method.

if ( CurrentBar < 2) return;

[antonek]

That is a bit hard nut to crack for me... I don't not understand why do I need to check "2 bars are in the high series" (not to mention the syntax of it). Is there any reference in help? Thanks

[NinjaTrader_AdamP]

antonek,

CurrentBar counts the number of OnBarUpdate() calls. When a strategy or indicator is attached to your chart, it begins at the first bar on your chart in the past. At this time, all the dataseries such as High, Low, etc. only have 1 element in them. If you try to look 1 bar into the past it won't exist until the next OnBarUpdate() call. Likely you are getting a run-time error of "Index out of bounds" and it's cancelling your strategy/indicator.

http://www.ninjatrader.com/support/helpGuides/nt7/index.html?currentbar.htm

http://www.ninjatrader.com/support/helpGuides/nt7/index.html?how_bars_are_built.htm

http://www.ninjatrader.com/support/helpGuides/nt7/index.html?multi_time_frame__instruments.htm