best way to detect a price crossing a line | Forex Factory

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best way to detect a price crossing a line

  • #1
  • First Post: Nov 24, 2011 2:44am Nov 24, 2011 2:44am
What is the best way to detect the event of the price crossing a horizontal line ? Just the comparison (current price) > (line value) wont work for me. I need to detect the actual moment when the price crosses the line from below to above and vice versa.
  • #2
  • Nov 24, 2011 2:53am Nov 24, 2011 2:53am
This code will do what you want for MA crossing, but can be adapted to your needs by changing the variable names. Please note that this works on the 2 previous bars and is intended to be used at the opening of a new bar. Again this may not be suitable for your needs, but should be simple to change.

PHP Code

      fastEMA1 = iMA (NULL, 0, FastEMAPeriod, 0, MODE_EMA, PRICE_TYPICAL, 1);
      fastEMA2 = iMA (NULL, 0, FastEMAPeriod, 0, MODE_EMA, PRICE_TYPICAL, 2);
      slowEMA1 = iMA (NULL, 0, SlowEMAPeriod, 0, MODE_EMA, PRICE_TYPICAL, 1);
      slowEMA2 = iMA (NULL, 0, SlowEMAPeriod, 0, MODE_EMA, PRICE_TYPICAL, 2);

      bool upBar1 = Close[1] > Open[1];
      bool downBar1 = Close[1] < Open[1];
      
      bool longEntry = upBar1 && fastEMA1 > slowEMA1 && fastEMA2 < slowEMA2;
      bool shortEntry = downBar1 && fastEMA1 < slowEMA1 && fastEMA2 > slowEMA2;
  • #3
  • Nov 24, 2011 3:59am Nov 24, 2011 3:59am
Thank you for the fast response. Unfortunately this will not work in my case, since this method always detects the cross in the past. The [0] bar might be a climax. The method I used is to store the last 2 Ask prices on each tick. If the last Ask is lower than the line and the latest Ask is higher than the line I consider this as a cross. The problem is that sometimes this method fails.

here is my code:

Inserted Code
   double ask1;
   double ask0;
...
int start() 
{
   ask1 = ask0;
   ask0 = Ask;
...
   if(ask0 < horizontalLine && ask1 > horizontalLine)
   {
        //OPEN ORDER
   }
  • #4
  • Nov 24, 2011 4:09am Nov 24, 2011 4:09am
you don't really seem to be defining your question well.

what doesn't work in storing the previous tick as being positively or negatively signed compared to the price level you are testing against and then comparing that to the current state?

if the last tick was above the line then the state is positive. if the current state is above the line it's still positive... therefore no cross has happened.

if the last tick was below, and current price is below... no change again.

if last tick was above or below, and current price is NOT the same then a cross has happened.

whatever happens you simply update the previous state with the current state for future tick comparisons.
Congratulations ScalaFX for coming out of the closet!
  • #5
  • Nov 24, 2011 4:12am Nov 24, 2011 4:12am
I have never coded this way, but of course it is possible to do. It will take some effort. The first thing I noticed about your code is that it doesn't handle the horizonalLine being equal to the Ask. That won't happen often, but has to be handled. You probably need to disregard that tick and not update Ask1.
  • #6
  • Nov 24, 2011 4:17am Nov 24, 2011 4:17am
Thanks again. Nubcake you are right, I can remove 1 of the variables. And Codemeister - it is possible the missing orders are caused by the Ask price being equal to the horizontal line value. I will run some tests.
  • #7
  • Last Post: Nov 24, 2011 4:29am Nov 24, 2011 4:29am
Quoting metyyyy
Thanks again. Nubcake you are right, I can remove 1 of the variables. And it is possible the 'not working' is caused by the Ask price being equal to the horizontal line value. I will run some tests.
in that case if i'm understanding you correctly then codemeister has alluded to the same issue.

this is all you need to do (as i see it).

Inserted Code
int laststate = 0;
double pricelevel;

bool function linecrossed() {
  int currentstate;
  bool r;

  currentstate = 0;  //neutral, or price is equal to the compared price
  if (Ask < pricelevel) currentstate = 1;  //is under price
  if (Ask > pricelevel) currentstate = 2;  //is above price

  if (laststate = 0) laststate = currentstate;  //if not yet initialized with a useful value 

  r = false;

  if (currentstate != laststate) r = true;

  laststate = currentstate;
  //if you don't want price touches then rebounds back to count as a cross then you would do the following instead
  //if (currentstate != 0) laststate = currentstate;

  return(r);
}

.....
  if ( linecrossed() ) { do stuff; }
.....
Congratulations ScalaFX for coming out of the closet!
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