How can I detect a specific TF to diff-TF change? Static doesn't work. | Forex Factory

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How can I detect a specific TF to diff-TF change? Static doesn't work.

  • #1
  • First Post: Sep 13, 2008 12:58pm Sep 13, 2008 12:58pm
Hi MT4 programmers,

When a user changes chart timeframe, all static variables are initialized once, and then the values are retained between function calls. However... what if what I want to retain is the current timeframe (Period()) value itself??

In the start() block, this code snippet shows how the "last_period" value is retained between ticks:
static int last_period;
Print("PRE-last_period: ", last_period);
last_period = Period();
Print("POST-last_period: ", last_period);

With the 1st tick, the PRE value is 0, and the POST value is, for example, 60. With every subsequent tick, both values are 60 as you would expect for a "static" variable.

However, what I need is when I change chart timeframes, with the first tick I would like to see a PRE value of "60" and a POST value of, for example, "240".

Unfortunately the PRE value is always "0". I also tried moving the "static int last_period;" line out of the start() block to make it a high-level global variable but that didn't work either. My program needs to know the timeframe was changed, including from what value. (If I go up in timeframes, my action will be different from when I go down in timeframe).

FYI, using a terminal client Global Variable isn't a practical answer, because I would need unique variables for every single chart. That's too many if I open up 20-30 charts.

I'm guessing my only answer would be to write the info to a unique file-per-chart (???), and read the file in the init() block. If so, does anyone have any examples? I've never attempted anything similar.

If there is an easier answer, I'd really like to know.

Thanks in advance for any help,
Pips4life (Kent)
  • #2
  • Edited 4:24pm Sep 13, 2008 4:08pm | Edited 4:24pm
Hi pips4life,

May be you can define two variables outside Start() (say "int LastChartTF, LastTickTF").

Inside the Start(), you can define what is LastChartTF as below (in this order):
PHP Code
if (LastTickTF != Period()) LastChartTF = LastTickTF; // LastChartTF will be updated only at start and at TF change. It will always remember the previous chart TF (at start it will be 0).
if (LastChartTF != 0 && LastTickTF != Period())  Print ("Chart TF has changed...");
LastTickTF = Period(); // this LastTickTF will be updated every tick. Any use of LastTickTF above this line will use the previous chart TF value at first tick, but will change to current TF in next tick.
Hope this helps/works!
chandra
PS: when you defined the variables outside Start(), you might have gotten correct result for just one tick after changing TF.
  • #3
  • Sep 13, 2008 5:14pm Sep 13, 2008 5:14pm
Quoting achandrasekaran99
Hi pips4life,

May be you can define two variables outside Start() (say "int LastChartTF, LastTickTF").

Inside the Start(), you can define what is LastChartTF as below (in this order):
PHP Code
if (LastTickTF != Period()) LastChartTF = LastTickTF; // LastChartTF will be updated only at start and at TF change. It will always remember the previous chart TF (at start it will be 0).
if (LastChartTF != 0 && LastTickTF != Period())  Print ("Chart TF has changed...");
LastTickTF = Period(); // this LastTickTF will be updated every tick. Any use of LastTickTF above this line will use the previous chart TF value at first tick, but will change to current TF in next tick.
Hope this helps/works!
chandra
PS: when you defined the variables outside Start(), you might have gotten correct result for just one tick after changing TF.

Hi Chandra,

Thanks for your attempt at a solution, but unfortunately I tried this approach and it still doesn't work.

The problem is that when you change timeframes, deinit() is called, and then so is the section outside of start(), and init() is called as well. AFAIK, changing timeframe is no different than removing the indicator and re-attaching it; or shutting down MT4 and restarting it. ALL the variables, including static ones -- and this is the problem -- are lost! The "last_*" variables -- whether static or not -- are all reset to 0, so they are not useful for comparing what was the last TF to the current TF.

In your original code, at start, "LastTickTF" = 0 and Period() is, say, 60, and so it sets LastChartTF = LastTickTF = 0 as well! (not 60!).

I noticed that error and tried changing your code to:
Quote
if (LastTickTF != Period()) LastChartTF = Period() ; // LastChartTF will be updated only at start and at TF change. It will always remember the previous chart TF (at start it will be 0).
if (LastChartTF != 0 && LastTickTF != Period()) Print ("Chart TF has changed FROM ...", LastTickTF, " to... ", Period() );
LastTickTF = Period(); // this LastTickTF will be updated every tick. Any use of LastTickTF above this line will use the previous chart TF value at first tick, but will change to current TF in next tick.

... but for the same reasons that variables are all initialized to zero when TF changes, it doesn't work either. The Print always says, "FROM... 0 to... XX". (If only it didn't say "0", my problem would be solved... sigh).

Any other ideas? (And thanks!)
Pips4life

P.S. I'm testing this on the weekend by simulating ticks with "Refresh". I think my testing is valid, but there's a possibility the solution won't work until charts are live. Just thought I'd mention this for full disclosure.
  • #4
  • Sep 13, 2008 5:51pm Sep 13, 2008 5:51pm
You'll need to either use a global variable or write the data to a file. Since the variable you used to store period() would also be reset, you'll have to escape the scope of init() and deinit() w/ something more universal... ie: a file or global variable.
  • #5
  • Sep 13, 2008 8:02pm Sep 13, 2008 8:02pm
Quoting Rabid
You'll need to either use a global variable or write the data to a file. Since the variable you used to store period() would also be reset, you'll have to escape the scope of init() and deinit() w/ something more universal... ie: a file or global variable.
I was hoping for a different answer although this is likely the way it is.

Can you point me to any examples of doing read/write to a file or files when the indicator is attached to several charts? I don't want to get trapped by "permission denied" problems when accessing files, and if possible, just for cleanliness I suppose, I'd like to avoid creating a unique filename for EVERY single chart.

Actually, for other purposes, I'm interested to know about how to use files to transfer data from one chart to another (to replicate objects). Any ideas or examples?

Thanks again,
Pips4life
  • #6
  • Sep 13, 2008 10:50pm Sep 13, 2008 10:50pm
Just use a filename based on symbol(). That'd create one for every pair you monitor, but not each timeframe. If that doesn't work you could read/write to a single csv file and just put the symbol() as a data field.

As long as you open, write/read, close quickly you won't have any problems... just make sure you handle a "can't open" error by checking for file existance, if it exists but can't be opened, then wait a little bit (100ms or so) and send it back to the open routine. Do a timeout count so if it goes beyond 100 attempts it'll error out or something.

Anyway I do something similar to the former, as I like to keep track of how many orders I've had for the day even if the EA gets restarted. Here's my code for that, could be adapted to keep track of the timeframe or to pass data back and forth between different copies of an EA/indi.

Inserted Code
int TodaysTradeCount() {
    // Is the data initialized?
    int FileHandle;
    string DailyCountFile = Symbol() + "_DailyCount.txt";
    if (CountInitialized == TRUE) {
         // Is it today's data?
         if (iTime(Symbol(),PERIOD_D1,0) > CurrentDay) {
              // No, update data.
              CountInitialized = TRUE;
              DailyCount = 0;
              CurrentDay = iTime(Symbol(),PERIOD_D1,0);

              // Write data to the file.
              FileHandle = FileOpen(DailyCountFile,FILE_CSV|FILE_WRITE,';');
              if (FileHandle < 1) {
                   // Couldn't write the file, error. Program needs to stop.
                   DailyCount = 9999;
                   return(DailyCount);
              }
              else {
                   // File is open, write data and close file.
                   FileWrite(FileHandle, DailyCount, CurrentDay);
                   FileClose(FileHandle);
              }
         }
         else {
              // Yes, we're good. NOP.
         }
    }
    else {
         // Attempt to open the file, does it open?
         FileHandle = FileOpen(DailyCountFile,FILE_CSV|FILE_READ,';');
         if (FileHandle < 1) {
              // Close the file jIc.
              // FileClose(FileHandle);

              // File problem, initialize the data.
              CountInitialized = TRUE;
              DailyCount = 0;
              CurrentDay = iTime(Symbol(),PERIOD_D1,0);
              
              // Write data to the file.
              FileHandle = FileOpen(DailyCountFile,FILE_CSV|FILE_WRITE,';');
              if (FileHandle < 1) {
                   // Couldn't write the file, error. Program needs to stop.
                   DailyCount = 9999;
                   return(DailyCount);
              }
              else {
                   // File is open, write data and close file.
                   FileWrite(FileHandle, DailyCount, CurrentDay);
                   FileClose(FileHandle);
              }
         }
         else {
              // File opened, read the data and close the file.
              DailyCount=FileReadNumber(FileHandle);
              CurrentDay=FileReadNumber(FileHandle);
              FileClose(FileHandle);

              // Is the data up to date?
              if (iTime(Symbol(),PERIOD_D1,0) > CurrentDay) {
                   // Old data, reset it.
                   CountInitialized = TRUE;
                   DailyCount = 0;
                   CurrentDay = iTime(Symbol(),PERIOD_D1,0);

                   // Write data to the file.
                   FileHandle = FileOpen(DailyCountFile,FILE_CSV|FILE_WRITE,';');
                   if (FileHandle < 1) {
                        // Couldn't write the file, error. Program needs to stop.
                        DailyCount = 9999;
                        return(DailyCount);
                   }
                   else {
                        // File is open, write data and close file.
                        FileWrite(FileHandle, DailyCount, CurrentDay);
                        FileClose(FileHandle);
                   }                   
              }
              else {
                   // Looks good.
                   CountInitialized = TRUE;
              }
         }
    }
    return(DailyCount);
}

void IncrementTodaysCount() {
    // Grab the current count.
    DailyCount = TodaysTradeCount();
    
    // Increment it.
    DailyCount++;

    // Write the file.
    int FileHandle;
    string DailyCountFile = Symbol() + "_DailyCount.txt";
    FileHandle = FileOpen(DailyCountFile,FILE_CSV|FILE_WRITE,';');
    if (FileHandle < 1) {
         // Couldn't write the file, error. Program needs to stop.
         DailyCount = 9999;
    }
    else {
         // File is open, write data and close file.
         FileWrite(FileHandle, DailyCount, CurrentDay);
         FileClose(FileHandle);
    }

    // Head on back.
    return;
}
  • #7
  • Sep 14, 2008 9:01pm Sep 14, 2008 9:01pm
Hi pips4life,

Sorry that my code piece did not work. By the way, the change you made is not correct and it should be left as such and another "if(LastChartTF == 0) LastChartTF=Period()" should have been added as second line. But that also would not have helped anyway.

So, the only options are writing in a file or using Global Variable. I also think Global Variable route seems complicated when used in many charts. The filewriting option I have not used but Rabid has described well. So, this file writing seem to be the only option but there also the file name may have problem when used in many charts (whatever solution is used there may even be used with GlobalVariable?). seems to be a new problem that needs a strategy to be developed.

Regards,
chandra
  • #8
  • Sep 15, 2008 12:01am Sep 15, 2008 12:01am
If you're running multiple charts per pair and need to track the TFs of each chart you're going to need a way to identify each chart individually. To do that you'll need another way to distinguish between the charts other than timeframe and symbol().

One way to do that might be an object that isn't deinitialized in the deinit(). You could look for a "chart name" object, if it isn't there, create one and put a random string in it. If it is there, read it in. Use that instead of symbol() for writing your chart. Since you don't deinitialize the object... it should stay there.

So then we can follow that logic a bit... instead of writing to a file (why, at this point?) why not just write the last TF to an object and not kill it in the deinit()? Wouldn't it just stay there to be read? As long as your creation of the object checks for it's existence first... you wouldn't create over it. Would you?
  • #9
  • Sep 15, 2008 6:27am Sep 15, 2008 6:27am
Quoting Rabid
If you're running multiple charts per pair and need to track the TFs of each chart you're going to need a way to identify each chart individually. To do that you'll need another way to distinguish between the charts other than timeframe and symbol().

One way to do that might be an object that isn't deinitialized in the deinit(). You could look for a "chart name" object, if it isn't there, create one and put a random string in it. If it is there, read it in. Use that instead of symbol() for writing your chart. Since you don't deinitialize the object... it should stay there.

So then we can follow that logic a bit... instead of writing to a file (why, at this point?) why not just write the last TF to an object and not kill it in the deinit()? Wouldn't it just stay there to be read? As long as your creation of the object checks for it's existence first... you wouldn't create over it. Would you?
Hi Rabid,

This seems to be a good idea. We can easily check and create new only when old is not there. Just TimeFrame can be used as name (or "TFChart-"+TF+"M" or more fancy). At each change we have to delete the old and make new with new info (never delete them in deinit). Instead of writing in a file or global variable, we would be writing it on the chart and reading it! The benefit is that there will not be any conflict with other chart data.

Regards,
chandra
  • #10
  • Sep 16, 2008 3:49am Sep 16, 2008 3:49am
Quoting Rabid
If you're running multiple charts per pair and need to track the TFs of each chart you're going to need a way to identify each chart individually. To do that you'll need another way to distinguish between the charts other than timeframe and symbol().

One way to do that might be an object that isn't deinitialized in the deinit(). You could look for a "chart name" object, if it isn't there, create one and put a random string in it. If it is there, read it in. Use that instead of symbol() for writing your chart. Since you don't deinitialize the object... it should stay there.

So then we can follow that logic a bit... instead of writing to a file (why, at this point?) why not just write the last TF to an object and not kill it in the deinit()? Wouldn't it just stay there to be read? As long as your creation of the object checks for it's existence first... you wouldn't create over it. Would you?

Hi Rabid,

I'm sure this idea to add an object with the timeframe is going to work. I just didn't think enough out of the box.

Thanks also for the code example. I'll get around to working with read/write of external files to transfer data at some point in the future... Thanks!

Pips4life

P.S. Thanks also to chandra for your help and interest in my question.
  • #11
  • Last Post: Sep 16, 2008 4:04am Sep 16, 2008 4:04am
Quoting Rabid
... if it exists but can't be opened, then wait a little bit (100ms or so) and send it back to the open routine. Do a timeout count so if it goes beyond 100 attempts it'll error out or something.
Hi Rabid,

One more question about your code to read/write files... what did you have in mind to cause the program to kill 100ms in between attempts? As an indicator, the Sleep() function is not supposed to work:

Quote
void Sleep(int milliseconds)The Sleep() function suspends execution of the current expert within the specified interval.
The Sleep() function cannot be called from custom indicators since they calculate in the interface thread and may not decelerate it.
The checking of the expert stop flag status every 0.1 second has been built into the function.
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