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Finding last two objects on chart, need help

  • #1
  • First Post: Sep 11, 2018 5:46pm Sep 11, 2018 5:46pm
Hello everyone,

I'm trying to get the last two objects from an indicator that draws horizontal trend lines on the chart, after searching the web, I came up with the following code to cycle through the objects on the current chart and choose the OBJ_TREND ones.
I have a problem with it, as it finds too many objects even when I limit it using StringFind().
I would also like to know if this code can be made simpler and or better (no OO, please, I'm not yet advanced enough to use OOP in MQL4), I thought about storing the Up trend lines on even indexes and the Down trend lines on odd indexes but until I've found out what's wrong with my code I'm using two arrays for simplicity.
I'm attaching a screenshot in which it is clearly seen that the if statements are also catching the "Buy" button, I don't know why, I looked at the examples and my code seems OK but is obviously not.

Thanks


Inserted Code
    double UpObjectsArray[][2];
    double DownObjectsArray[][2];
    int total=ObjectsTotal(0,0,OBJ_TREND);
    if(total>1)
    {
      ArrayResize(UpObjectsArray,total);
      ArrayResize(DownObjectsArray,total);
      for(int i=0; i<total; i++)
      {
        string name=ObjectName(i);
        if (StringFind(name, "prob_U", 0) > -1)
        {
          UpObjectsArray[i][0]=ObjectGet(name,OBJPROP_PRICE1);
          UpObjectsArray[i][1]=i;
        }
        if (StringFind(name, "prob_D", 0) > -1)
        {
          DownObjectsArray[i][0]=ObjectGet(name,OBJPROP_PRICE1);
          DownObjectsArray[i][1]=i;
        }
      }
    }
    ArraySort(UpObjectsArray,MODE_DESCEND);
    ArraySort(DownObjectsArray,MODE_DESCEND);
    for(int i=0; i<total; i++)
    {
      Alert("i1: "+" ObjectName: "+ObjectName(UpObjectsArray[i][1])+" Price: "+UpObjectsArray[i][0]);
      Alert("i2: "+" ObjectName: "+ObjectName(DownObjectsArray[i][1])+" Price: "+DownObjectsArray[i][0]);
    }
Attached Image(s) (click to enlarge)
Click to Enlarge Name: Capture.PNG Size: 82 KB
Click to Enlarge Name: Capture1.PNG Size: 51 KB
  • #2
  • Sep 11, 2018 10:30pm Sep 11, 2018 10:30pm
1)
When your code does: total=ObjectsTotal(0,0,OBJ_TREND);
... your expect that the count is of only OBJ_TREND type, right?

Why then would you access each object using only: ObjectName(i)
... which is irrespective of ObjType ?? That would be wrong, and is why you are ending up with non-TrendLine objects, and you're missing a few you want to check.

I have only used the ",OBJ_TREND" argument to see if >= 1 of some object type exists, and if it does, I cycle through 100% of objects to find the few I want using a test that does:
objName = ObjectName(i);
objType = ObjectType(objName);
if( objType == OBJ_TREND) ...". // I've used this method a lot.

However, even though it's not yet documented in my MT4 Reference manual, by a syntax-bubble-popup, I now see that there appear to be *two* syntax forms for ObjectName.

You probably can use a new form I was not aware of:
Replace every occurrence of: ObjectName(arg)
with: ObjectName(arg,0,OBJ_TREND)

I would assume that with this syntax, the "arg" is indexed for the subset of objects that are OBJ_TREND, in the same way that "ObjectsTotal(0,0,OBJ_TREND)" counts them. If true, you can use this approach. If not true, cycle through 100% of objects.


2) You wrote: "I'm trying to get the last two objects from an indicator that draws horizontal trend lines on the chart"

A) Why are you bothering to store-and-sort by Price? If you want the "lowest" or the "highest", then sure. But you said "last", which is time-based.
Shouldn't you be storing and sorting by TIME1 (or TIME2, or the latest of either??) ?

You are also storing into two arrays, so I suspect you probably want the most recent of each matching pattern, right?

B) I question why you would "ArrayResize(arrayname,total);" ... when "total" is more objects than you intend to store? You might have a huge number of trendlines, yet only a handful that match your StringFind criteria.

Rather, initialize some counter of *found* objects: int_foundcnt=0;
You increment the counter if/when you find something, then you ArrayResize up-by-one (as necessary), then store it.
In the end, you have found "foundcnt" number of objects, and sorting a smaller array would be faster.

C) However, why bother to store-and-SORT-in-arrays at all? Storing a lot just to get two extreme items is a waste of memory. Sorting is probably slower than just comparing real-time. It also seems to me a waste to store the time(or price) of every object, then sort them, if all you want are just the two that are extremes.

If you just want to find two extremes (of the *same* list of objects), you could cycle and store and test for each object you find.

Something like:
datetime firstObjTime=0, secondObjTime=0, thisObjTime;
string firstObjName="", secondObjName="";

for(i=0; i<total; i++)
{
objName = ObjectName(i,0,OBJ_TREND);
if (StringFind(objName, "prob_U", 0) > -1)
{
thisObjTime = ObjectGet(objName,OBJPROP_TIME1);
if( thisObjTime > firstObjTime) { firstObjTime = thisObjTime; firstObjName = objName; }

// Get the 2nd object less than the 1st, or "==" to the 1st, if it's a different object than the 1st)
if( thisObjTime > secondObjTime && ( thisObjTime < firstObjTime || ( thisObjTime == firstObjTime && objName != firstObjName ) ) )
{ secondObjTime = thisObjTime; secondObjName = objName; }
}
}


You get the idea above. If you only want the most recent "prob_U" object, then you wouldn't need any of the "secondObj*" stuff above.
Just use the same idea twice to find the most recent "prob_U" object, and similarly, the most recent "prob_D" object.


I didn't compile or code check anything I wrote above. No doubt I made typos or errors, but I've given the outline how to go about it.

Good luck.
  • #3
  • Sep 12, 2018 12:59am Sep 12, 2018 12:59am
Inserted Code
double UpObjectsArray[][2]; double DownObjectsArray[][2]; int total=ObjectsTotal(0,0,OBJ_TREND); if(total>1) { ArrayResize(UpObjectsArray,total); ArrayResize(DownObjectsArray,total); for(int i=0; i<total; i++) { string name=ObjectName(i); if (StringFind(name, "prob_U", 0) > -1) { UpObjectsArray[i][0]=ObjectGet(name,OBJPROP_PRICE1); UpObjectsArray[i][1]=i; } if (StringFind(name, "prob_D", 0) > -1) { DownObjectsArray[i][0]=ObjectGet(name,OBJPROP_PRICE1); DownObjectsArray[i][1]=i; } } } ArraySort(UpObjectsArray,MODE_DESCEND); ArraySort(DownObjectsArray,MODE_DESCEND); for(int i=0; i<total; i++) { Alert("i1: "+" ObjectName: "+ObjectName(UpObjectsArray[i][1])+" Price: "+UpObjectsArray[i][0]); Alert("i2: "+" ObjectName: "+ObjectName(DownObjectsArray[i][1])+" Price: "+DownObjectsArray[i][0]); }
your code
Inserted Code
double UpObjectsArray[][2]; double DownObjectsArray[][2]; int total=ObjectsTotal(0,0,OBJ_TREND); if(total>1) { ArrayResize(UpObjectsArray,total); ArrayResize(DownObjectsArray,total); for(int i=0; i<total; i++) { string name=ObjectName(i); if (StringFind(name, "prob_U", 0) > -1) { UpObjectsArray[i][0]=ObjectGet(name,OBJPROP_PRICE1); UpObjectsArray[i][1]=i; } if (StringFind(name, "prob_D", 0) > -1) { DownObjectsArray[i][0]=ObjectGet(name,OBJPROP_PRICE1); DownObjectsArray[i][1]=i; } } } ArraySort(UpObjectsArray,MODE_DESCEND); ArraySort(DownObjectsArray,MODE_DESCEND); for(int i=total-2; i<total; i++) { Alert("i1: "+" ObjectName: "+ObjectName(UpObjectsArray[i][1])+" Price: "+UpObjectsArray[i][0]); Alert("i2: "+" ObjectName: "+ObjectName(DownObjectsArray[i][1])+" Price: "+DownObjectsArray[i][0]); }
is that what you want?
Profit growth tells you the trader ability.
  • #4
  • Sep 12, 2018 1:31am Sep 12, 2018 1:31am
Thank you for replying.
Quoting pips4life
1)
When your code does: total=ObjectsTotal(0,0,OBJ_TREND);
... your expect that the count is of only OBJ_TREND type, right?
Yes, I am
Quoting pips4life
Why then would you access each object using only: ObjectName(i)
... which is irrespective of ObjType ?? That would be wrong, and is why you are ending up with non-TrendLine objects, and you're missing a few you want to check.
Because if all the objects are OBJ_TREND than I can search through the names and only get the OBJPROP_PRICE1 I need, or at least, that's what I thought would be easiest
Quoting pips4life
I would assume that with this syntax, the "arg" is indexed for the subset of objects that are OBJ_TREND, in the same way that "ObjectsTotal(0,0,OBJ_TREND)" counts them. If true, you can use this approach. If not true, cycle through 100% of objects.
It does, according to the MQL Editor version I'm using and Alert-ing the objName finds only the prob_U and prob_D I need
Quoting pips4life
2) You wrote: "I'm trying to get the last two objects from an indicator that draws horizontal trend lines on the chart"
A) Why are you bothering to store-and-sort by Price? If you want the "lowest" or the "highest", then sure. But you said "last", which is time-based.
Shouldn't you be storing and sorting by TIME1 (or TIME2, or the latest of either??) ?
There are two "interesting" objects for me, the last prob_D and the last prob_U, I'll probablly only need one but for the time being, I'd like to get both, both prob_D and prob_U hold a price level I am interested in, I don't care about the time so I only index the price
Quoting pips4life
B) I question why you would "ArrayResize(arrayname,total);" ... when "total" is more objects than you intend to store? You might have a huge number of trendlines, yet only a handful that match your StringFind criteria.
Indeed, and I have discarded the use of arrays completely as per your suggestion
Quoting pips4life
C) However, why bother to store-and-SORT-in-arrays at all? Storing a lot just to get two extreme items is a waste of memory. Sorting is probably slower than just comparing real-time. It also seems to me a waste to store the time(or price) of every object, then sort them, if all you want are just the two that are extremes.
If you just want to find two extremes (of the *same* list of objects), you could cycle and store and test for each object you find.
Something like:
Thanks, I have amended my code to look like this but I now get the "Buy" as the only match for name but getting the correct price level, maybe I can work with that but I don't like it because maybe another indicator would have another object interfering with the code, resulting in a different price level
Inserted Code
    datetime firstObjTime=0, secondObjTime=0, thisObjTime;
    string firstObjName="", secondObjName="";
    string objName, thisObjName;
    int objType;
    
    int total=ObjectsTotal(0, 0, OBJ_TREND);
    if(total>=1)
    {
      for(int i=0; i<total; i++)
      {
        objName=ObjectName(0, i, 0, OBJ_TREND);
        if (ObjectType(objName) == OBJ_TREND)
        {
          if (StringFind(objName, "prob_U", 0) > -1 )
          {
            thisObjTime = ObjectGet(objName,OBJPROP_TIME1);
            if( thisObjTime > firstObjTime)
            {
              firstObjTime = thisObjTime;
              firstObjName = objName;
            }
          }
        }
      }
    }
    Alert("ObjectName: "+ObjectName(objName)+" Price: "+ObjectGet(objName, OBJPROP_PRICE1));
Attached Image (click to enlarge)
Click to Enlarge Name: Capture.PNG Size: 73 KB
  • #5
  • Sep 12, 2018 1:34am Sep 12, 2018 1:34am
Quoting voketexpert
double UpObjectsArray[][2]; double DownObjectsArray[][2]; int total=ObjectsTotal(0,0,OBJ_TREND); if(total>1) { ArrayResize(UpObjectsArray,total); ArrayResize(DownObjectsArray,total); for(int i=0; i<total; i++) { string name=ObjectName(i); if (StringFind(name, "prob_U", 0) > -1) { UpObjectsArray[0]=ObjectGet(name,OBJPROP_PRICE1); UpObjectsArray[1]=i; } if (StringFind(name, "prob_D", 0) > -1) { DownObjectsArray[0]=ObjectGet(name,OBJPROP_PRICE1); DownObjectsArray[1]=i; } } } ArraySort(UpObjectsArray,MODE_DESCEND); ArraySort(DownObjectsArray,MODE_DESCEND);...
Thanks for replying.

Why using total-2?
And this code finds the "Buy", as well
Attached Image (click to enlarge)
Click to Enlarge Name: Capture.PNG Size: 69 KB
  • #6
  • Sep 12, 2018 1:46am Sep 12, 2018 1:46am
Subs. Thanks and
Regards
  • #7
  • Sep 12, 2018 12:18pm Sep 12, 2018 12:18pm
Quoting Reamasesa
Thank you for replying...
You're almost there but you have some obvious mistakes.

You have the line:
Alert("ObjectName: "+ObjectName(objName)+" Price: "+ObjectGet(objName, OBJPROP_PRICE1));

You used the loop to find a single object (firstObjName) and now... you never use what you found??! You should not be referring to the final result as "objName" at all, which would be the last matching object checked by the loop (which may or may not be the same as the right answer; you're just lucky if it is). Rather use the one the loop actually found, which is "firstObjName".

Assuming you correct that first problem: Why would you try to use "ObjectName(firstObjName)"?? You already have the name! Use "firstObjName".

In your (wrong) code, the conversion of the string in the variable to a number likely resulted in "0" which would be the same as doing "ObjectName(0)", which is not the object you want.


No doubt when you compiled your code, you got a warning which gave you a clue:

implicit conversion from 'string' to 'number'

If you had double-clicked on that warning, it would take you right to the line# that caused it. (And, it even tells you the column number too).

Try to fix, or at least understand, every single warning and error when you compile.

Corrected:
Alert("ObjectName: "+firstObjName+" Price: "+ObjectGet(firstObjName, OBJPROP_PRICE1));

When you get the code working to find the "prob_U" object, copy the "U" section, paste it, then modify the "U" variables to be specific for "D" purposes.

I suggest you use more specific variable names for the "U" section, and then trivially copy-and-edit to make the "D" section.

Instead of "firstObjName" (it's not really "first", but rather "latest"), find "latestObjNameU" and then for the other section, use "latestObjNameD".
Instead of "firstObjTime", use "latestObjTimeU", and then for the other section, use "latestObjTimeD".

When you're code is changed, you'll check your result with something like:
Alert("ObjectName_U: "+latestObjNameU+" Price: "+ObjectGet(latestObjNameU, OBJPROP_PRICE1));
Alert("ObjectName_D: "+latestObjNameD+" Price: "+ObjectGet(latestObjNameD, OBJPROP_PRICE1));
  • #8
  • Sep 12, 2018 4:26pm Sep 12, 2018 4:26pm
Quoting pips4life
{quote} You're almost there but you have some obvious mistakes.
Considering the fact that I can't code for my life, than "obvious" is not a word I would choose to describe my head-banging-against-the-wall mistakes
Thanks for correcting my code and for your insights.

I thought about what you said earlier and you are correct, I don't need all that information as I only want the OBJPROP_PRICE1 of the latest trendline object so there is no need to find the last two objects, only one and since I don't care about the name, I'm only using it for sifting through the objects and that's it, I hope my code below is better and more logical, I tried to construct it as clean and readable as I could.
You were bang on regarding the "Buy" object as it was the last object that got scanned, didn't match but was stored as objName, once I figured it out writing the rest of the routine was easier, if you'd be kind enough to review it, it would be greatly appreciated.


Again, thanks for all your help with this, I have lost more than one sleep cycle over it.
Thank you.


Inserted Code
      datetime UpObjTime=0,DownObjTime=0,thisObjTime=0;
      string UpObjName="",DownObjName="";
      string objName;
      int total=ObjectsTotal(0, 0, OBJ_TREND);
      if(total>=1)
      {
        for(int i=0; i<total; i++)
        {
          objName=ObjectName(0,i,0,OBJ_TREND);
          if(ObjectType(objName)==OBJ_TREND)
          {
            if(StringFind(objName,"prob_U",0)>-1)
            {
              thisObjTime=datetime(ObjectGet(objName,OBJPROP_TIME1));
              if(thisObjTime>UpObjTime)
              {
                UpObjTime = thisObjTime;
                UpObjName = objName;
                UpPrice = ObjectGet(UpObjName, OBJPROP_PRICE1);
              }
            }
            if(StringFind(objName,"prob_D",0)>-1)
            {
              thisObjTime=datetime(ObjectGet(objName,OBJPROP_TIME1));
              if(thisObjTime>DownObjTime)
              {
                DownObjTime = thisObjTime;
                DownObjName = objName;
                DownPrice = ObjectGet(DownObjName, OBJPROP_PRICE1);
              }
            }
          }
        }
        if(DownObjTime>UpObjTime)
        {
          Alert("Down rulz at: "+DoubleToString(DownPrice));
        }
        if(DownObjTime<UpObjTime)
        {
          Alert("Up rulz at: "+DoubleToString(UpPrice));
        }
      }
Attached Image (click to enlarge)
Click to Enlarge Name: Capture.PNG Size: 55 KB
  • #9
  • Sep 12, 2018 7:54pm Sep 12, 2018 7:54pm
Quoting Reamasesa
{quote} Considering the fact that I can't code for my life, than "obvious" is not a word I would choose to describe my head-banging-against-the-wall mistakes Thanks for correcting my code and for your insights. ...
I helped you and gave you tips because at least you tried to code it yourself. I can respect that. You will learn more if I only give suggestions and not just do it for you.

If I were starting out today and wanted to learn MQL4, I would probably pay for the courses at learnmql4 dot com. (I have no affiliation, and I've not taken the courses myself, but based on his style observed in a few freebies on youtube, I like it and could have saved myself a lot of time. No doubt, I could learn a few more tricks from him, but for now I know enough).

Your code looks fine. The way it's structured in two sections gives you some flexibility if you ever want more than one line at a time.

But if you truly only want one line, ever, you could have done a single section with an object search like:
if(StringFind(objName,"prob_U",0)>-1 || if(StringFind(objName,"prob_D",0)>-1) ...

Or if you keep it the way it is, you might as well put an "else" before the 2nd "if(StringFind..." because if the 1st section is true, the 2nd will never be.

Is "prob_U" in the *middle* of the ObjectName you're looking for? Or does it begin with exactly that string?
If in the middle, then no change. But if it begins with exactly that, your StringFind's could have used "==0" instead of ">-1"

It's working for you now. Nothing but minor suggestions for you. Good job.
  • #10
  • Sep 12, 2018 10:12pm Sep 12, 2018 10:12pm
Quoting pips4life
{quote} I helped you and gave you tips because at least you tried to code it yourself. I can respect that. You will learn more if I only give suggestions and not just do it for you. If I were starting out today and wanted to learn MQL4, I would probably pay for the courses at learnmql4 dot com. (I have no affiliation, and I've not taken the courses myself, but based on his style observed in a few freebies on youtube, I like it and could have saved myself a lot of time. No doubt, I could learn a few more tricks from him, but for now I know enough)....
I have to respectfully disagree with the recommendation for the Learn MQL4 course. MQL4 is quickly becoming irrelevant as MT4 is already end of life and brokers are beginning to switch to MT5 or even better platforms / APIs. If your target is to eventually migrate to anything other than than MT4 then you need to have a fundamental understanding of OOP. Even if your short-term target is to get a bit of use out of MT4 you still should know OOP concepts since it's also available in MT4 -- and consequently would make light work of your current programming challenge. It's imperative that the time you invest into your education is not wasted on obsolete language/patterns, rather, a quality base that can be easily transferred to other languages including MQL4.

FWIW, I learned MQL as my first language and my biggest regret is not learning C++ first. All of the MQL courses (I've seen) and 90% of open-source MQL will teach you some really bad habits, and if you ever hope to move to a different language not only will you have to learn correct programming concepts/patterns all over again, but you'll also have to unlearn your bad habits. If I had to do it all over again (now), I'd learn C++ (basics not libraries), OOP concepts, and some basic design patterns before diving into some good MQL5/4 examples. Just my two cents anyway.
  • #11
  • Sep 12, 2018 11:14pm Sep 12, 2018 11:14pm
Trading System Applications in places like Credit Suisse , UBS , Lehman Brothers, BNP Paribas were in mainly in c language as there was no c++ language before 1984. Most Trading Systems used a variety of languages including Microsoft Excel Macros , Visual Basic on Trading floors. About 1985-1986 was the advent of c++ and OOP was more an invention of the 1990's , applications such as MQL4 could not have been written or used. The physical hardware was also in question as well.
OOP is fairly new and Metatrader language was only started and a stream lined version of the c language. Its current move to c++ is only a catch up with the now stable OOP of c++. Some elements of still exist in c++ OOP. Unavoidable.
  • #12
  • Sep 12, 2018 11:52pm Sep 12, 2018 11:52pm
Quoting Emma1
Trading System Applications in places like Credit Suisse , UBS , Lehman Brothers, BNP Paribas were in mainly in c language as there was no c++ language before 1984. Most Trading Systems used a variety of languages including Microsoft Excel Macros , Visual Basic on Trading floors. About 1985-1986 was the advent of c++ and OOP was more an invention of the 1990's , applications such as MQL4 could not have been written or used. The physical hardware was also in question as well. OOP is fairly new and Metatrader language was only started and a stream...
Nowadays, most quant shops prototype and test in python then port the HFT stuff over to C++. HFT optimized code makes use of a lot of low-level concepts at the expense of developer convenience. Since no retail trader could ever dream of competing in the HFT space, they're are better off utilizing high-level languages and design patterns in order to optimize the devops cycle.
  • #13
  • Sep 13, 2018 3:57am Sep 13, 2018 3:57am
Quoting Nicholishen
{quote} I have to respectfully disagree with the recommendation for the Learn MQL4 course. MQL4 is quickly becoming irrelevant as MT4 is already end of life and brokers are beginning to switch to MT5 or even better platforms / APIs. If your target is to eventually migrate to anything other than than MT4 then you need to have a fundamental understanding of OOP...
I agree with you on the value of OOP (which I still know very little of, but am open to learn). When I made the recommendation, I knew it wasn't going to focus on OOP style very much, but the OP wrote "(no OO, please, I'm not yet advanced enough to use OOP in MQL4)".

It's a really high bar to go from not being a programmer at all to doing OOP.

The Learn MQL4 course does teach C-style pretty well, and it's easiest for most.
While the syllabus says the course touches on OOP, I'm under the impression it is minimal and not focused on. (Maybe I'm wrong).

I always like seeing the OOP examples you post, but there's still plenty I don't understand when I just read some of them, let alone write some myself.

Where would you suggest to learn not only generic OOP concepts, but specific examples and training focused on writing specifically MQL5(4) OOP style?
  • #14
  • Last Post: Sep 13, 2018 10:44am Sep 13, 2018 10:44am
Quoting pips4life
{quote} I agree with you on the value of OOP (which I still know very little of, but am open to learn). When I made the recommendation, I knew it wasn't going to focus on OOP style very much, but the OP wrote "(no OO, please, I'm not yet advanced enough to use OOP in MQL4)". It's a really high bar to go from not being a programmer at all to doing OOP. The Learn MQL4 course does teach C-style pretty well, and it's easiest for most. While the syllabus says the course touches on OOP, I'm under the impression it is minimal and not focused on. (Maybe...
There's many online C++ tutorials... I used solo-learn because they have a really nice android app and I could learn any-where/time. learncpp.com is also a very good resource (probably the best). Once you get a handle on the concepts then just crack open the include folder and start going through the standard library.
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