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How to store and change a value?

  • #1
  • First Post: Jul 22, 2008 1:38pm Jul 22, 2008 1:38pm
I am still trying to get an indicator im making to calculate correctly. I have been given great help from some other members here, and made great progress.
It is kind of working but not exactly how I wanted it to calculate.
I have come up with a new way of doing it but I have a problem with storing a variable and then changing that stored value. This will finally get it working exatcly how I want it to if its even possible to do so. I am told anything is possible with coding.

Basically I need to find out the difference in ask price on one bar to next ask price on next bar. So i do bar1 - bar2 to get the difference. I would then like to store this value. When bar 0 closes and a new bar comes in I want to calculate once again the new bar1 and bar2 difference, so doing the above calculation on these bars.
I then want to add this new value to the stored value before. Lets say the first bar1 and bar2 had a difference of 5 pips. The new bar1 and bar 2 has a difference of 10 pips.
So old stored value (5) + new value (10) = new stored value (15).
I would then like to loop through this for each new bar that closes, just adding to the stored value the difference between the new bar1 and bar2.

The way i imagine the line to look is when indicator is started it starts at a value of 0 as nothing has been calculated. Then it calculates bar1 and bar2 to give eg 5. new bar comes in, do same again but add this to previous value eg 15 etc for each new bar. So say now 10 new bars has come in since the start of indicator, the value has gone from 5 to 15,30,12, -4, -20, 2... etc.

Again help always appreciated.
  • #2
  • Jul 22, 2008 1:44pm Jul 22, 2008 1:44pm
Ask price of the bar at which point? the open or the close? I'm sure you're aware that prices move with a bar. so... where in the bar you wanna record?
Programming for a better future.
  • #3
  • Jul 22, 2008 2:07pm Jul 22, 2008 2:07pm
yes sorry. it would be at the close of the bar, so the close price is what i shud have said.
  • #4
  • Jul 22, 2008 2:09pm Jul 22, 2008 2:09pm
Quoting fry2010
yes sorry. it would be at the close of the bar, so the close price is what i shud have said.
its actually a easier to code if you do the calculation at the opening of a new bar. assuming in general, the opening of the current bar usually equals to the closing of the previous bar.
Programming for a better future.
  • #5
  • Jul 22, 2008 2:12pm Jul 22, 2008 2:12pm
you say easier? this seems hard to me at best. i wudnt mind doing it at the open of bar at all, like you say they are effectivly the same.
  • #6
  • Jul 22, 2008 2:18pm Jul 22, 2008 2:18pm
do you want the diff between 2 ask prices to be in absolute value? as in if it turns out to be negative, change it to positive. and do you want that diff to be in pips? as in the value is an int instead of double.
Programming for a better future.
  • #7
  • Jul 22, 2008 2:23pm Jul 22, 2008 2:23pm
Inserted Code
datetime lastCalculationTime;
double ask1 = 0;
double ask2 = 0;
bool calculationStarts = false;
int totaldiff = 0;
//+------------------------------------------------------------------+
//| expert initialization function                                   |
//+------------------------------------------------------------------+
int init()
{
//----
   lastCalculationTime = TimeCurrent();
//----
   return(0);
}
//+------------------------------------------------------------------+
//| expert deinitialization function                                 |
//+------------------------------------------------------------------+
int deinit()
{
//----
   
//----
   return(0);
}
//+------------------------------------------------------------------+
//| expert start function                                            |
//+------------------------------------------------------------------+
int start()
{
//----
   int currentdiff = 0;
   if (Time[0] > lastCalculationTime)
   {
      if (!calculationStarts)
      {
         ask1 = Ask;
         lastCalculationTime = TimeCurrent();
         calculationStarts = true;
      }
      else
      {
         ask2 = ask1;
         ask1 = Ask;
         currentdiff = (MathAbs(ask1 - ask2)) / Point;
         totaldiff = totaldiff + currentdiff;
      }
   }
//----
   return(0);
}
//+------------------------------------------------------------------+
Programming for a better future.
  • #8
  • Jul 22, 2008 2:24pm Jul 22, 2008 2:24pm
I only say its easier cos I do all my calculations at the start of a candle. and cos if you were to use Close[0], you'll still need to add in spread since the chart only display in bid prices.
Programming for a better future.
  • #9
  • Jul 22, 2008 2:27pm Jul 22, 2008 2:27pm
lol, there are choices? whatever is easiest really. although if it is negative can u make it show negative? i just thought about it and what i think it to look like would be a mini line chart of the actual main chart.
  • #10
  • Jul 22, 2008 2:28pm Jul 22, 2008 2:28pm
do you need me to explain the codes?
Programming for a better future.
  • #11
  • Jul 22, 2008 2:30pm Jul 22, 2008 2:30pm
Quoting fry2010
lol, there are choices? whatever is easiest really. although if it is negative can u make it show negative? i just thought about it and what i think it to look like would be a mini line chart of the actual main chart.
just to confirm, you want the new Ask to minus the previous Ask?

and again, you want it to be "integer" or "double" value?

integer for pip difference
double for price difference
Programming for a better future.
  • #12
  • Jul 22, 2008 2:32pm Jul 22, 2008 2:32pm
ok that was fast. No i wont bother you for explanation you have been very helpfull. I will study it i kind of understand it as it is. If I put it in as an indicator which variable do I set to extmapbuffer?
  • #13
  • Jul 22, 2008 2:35pm Jul 22, 2008 2:35pm
yes that is right, current ask minus previous ask. um could it be double type data? also does it continue to add to the last value so basically it will keep adding the difference to the previous total difference?
  • #14
  • Jul 22, 2008 2:36pm Jul 22, 2008 2:36pm
Quoting fry2010
ok that was fast. No i wont bother you for explanation you have been very helpfull. I will study it i kind of understand it as it is. If I put it in as an indicator which variable do I set to extmapbuffer?
I believe what you want is the sum of all diff? that would be totaldiff. and wait, let me make the amendments first.

I take it as you want it to be in integer. pip difference.

sorry. double value it is. price difference
Programming for a better future.
  • #15
  • Jul 22, 2008 2:44pm Jul 22, 2008 2:44pm
Inserted Code
 
datetime lastCalculationTime;
double ask1 = 0;
double ask2 = 0;
bool calculationStarts = false;
double totaldiff = 0;
//+------------------------------------------------------------------+
//| expert initialization function                                   |
//+------------------------------------------------------------------+
int init()
{
//----
   lastCalculationTime = TimeCurrent();
//----
   return(0);
}
//+------------------------------------------------------------------+
//| expert deinitialization function                                 |
//+------------------------------------------------------------------+
int deinit()
{
//----
 
//----
   return(0);
}
//+------------------------------------------------------------------+
//| expert start function                                            |
//+------------------------------------------------------------------+
int start()
{
//----
   double currentdiff = 0;
   if (Time[0] > lastCalculationTime)
   {
      if (!calculationStarts)
      {
         ask1 = Ask;
         lastCalculationTime = TimeCurrent();
         calculationStarts = true;
      }
      else
      {
         ask2 = ask1;
         ask1 = Ask;
         currentdiff = ask1 - ask2;
         totaldiff = totaldiff + currentdiff;
         lastCalculationTime = TimeCurrent();
      }
   }
//----
   return(0);
}
//+------------------------------------------------------------------+

yes it will continue to add the difference as long as your indicator is running non stop. but it'll start at 0 again when you re-initialise it.

Inserted Code
totaldiff = totaldiff + currentdiff;

take note of the global variables

Inserted Code
datetime lastCalculationTime;
double ask1 = 0;
double ask2 = 0;
bool calculationStarts = false;
double totaldiff = 0;

and the line of code in the init function

Inserted Code
int init()
{
//----
   lastCalculationTime = TimeCurrent();
//----
   return(0);
}

actually... come to think of it, I'm not sure how you're going to put these values in the ExtMapBuffer. unless you code in a way, your buffer array keeps pushing its values backwards so you'll be able to record the new value in ExtMapBuffer[0].

***EDIT***
just added lastCalculationTime = TimeCurrent(); into the else block too. that should do the trick.

PM me if you ran into trouble. goodnight.
Programming for a better future.
  • #16
  • Jul 22, 2008 2:51pm Jul 22, 2008 2:51pm
ok will give it a shot. i cant beleive iv been racking my brains over this for weeks and you read what i wanted in what 20-30 mins and have coded already? Thanks a lot for all your help zen, goodnight.
  • #17
  • Jul 22, 2008 3:07pm Jul 22, 2008 3:07pm
at the moment im struggling to get a reading on the indicator. But maybe I have to wait for a new bar to form? i will try that.
  • #18
  • Jul 22, 2008 3:16pm Jul 22, 2008 3:16pm
the more you do, the easier it comes to you I promise. =)

having said that, I'm more of an EA guy than an indicator person. so I'm not sure about some things.

but according to the documentation...

Data buffer is almost a simple array. Its peculiarity is in the fact that this array is partially managed by the terminal. The terminal changes the array so, that at the receipt of each new bar, a shift takes place.

if that's the case, the shifting is automatically done by MT4, all you need to do is place the new totaldiff value in ExtMapBuffer[0]. I could be wrong.

goodnight again. geez.. its almost good morning... haha.
Programming for a better future.
  • #19
  • Jul 22, 2008 3:21pm Jul 22, 2008 3:21pm
Quoting fry2010
at the moment im struggling to get a reading on the indicator. But maybe I have to wait for a new bar to form? i will try that.
yes, I code it in such a way that the storing of first value starts on the next candle, and the calculation will only commence on the 3rd candle counting from the time you attach the indicator.

I didn't code it to use the immediate candle since I want consistency, as in always wait till a candle open before doing anything. and I don't reckon we'll be able to time the attaching of indicator to chart right at the point of opening... I hope you get what i mean.

I can code it to retrieve the Open[0] of the first candle it sees, but again, that's really the bid price and spread needs to be added to it to get the Ask. and we all know how spreads can widen at times... its hard to tell.

test on 1m charts. its faster to see the results that way (if there's anything to show at all that is).
Programming for a better future.
  • #20
  • Jul 22, 2008 3:24pm Jul 22, 2008 3:24pm
oh. and. good luck.
Programming for a better future.
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