2D array help needed...

MartinS13X 2023.01.16 06:33

You probably get a billion questions about arrays, and I feel like I've read a billion pages on them.

But I'm getting a tad annoyed. I didn't think i was this stupid, but somewhere I'm going wrong.

All I want to do is declare a 2D array with three variables stored in it.
The bar number at a particular swing (from zigzag) and the price associated with that bar/swing

Now, I thought I followed https://book.mql4.com/variables/arrays pretty neatly but still I'm getting all sorts of errors

Here's an example of what I think i'm trying to do:

 int   x=0;
      int   y=0;
      double   z=0;
      
      double Array[x][y][z];    //[Bars][SwingNr][Price]
      ArrayInitialize (Array,0);
      ArrayResize(Array,Bars);
              
              int value = 1;
              int othervalue = 2;
              double  price = 1.2345;

              Array[x]=value;
              Array[y]=othervalue;
              Array[z]=price;

Now, as far as I can tell, that SHOULD work... but it doesn't.

I'm getting these errors:

'[' - invalid index value 49 27

'[' - invalid index value 49 30

'[' - invalid index value 49 33

truncation of constant value 55 27

'x' - integer expression expected 56 21

'Array' - invalid array access 56 15

'y' - integer expression expected 57 21

'Array' - invalid array access 57 15

'z' - integer expression expected 58 21

'Array' - invalid array access 58 15

(if you want, I can post the actual code, but figured this is a bit clearer)

Arrays - Variables - MQL4 Tutorial

book.mql4.com

Arrays - Variables - MQL4 Tutorial

Keith Watford 2023.01.16 06:51 #1

MartinS13X:

Now, as far as I can tell, that SHOULD work... but it doesn't.

      int   x=0;
      int   y=0;
      double   z=0;  //Why is this a double?
      
      double Array[x][y][z];    //[Bars][SwingNr][Price]

This is the same as

double Array[0][0][0];

You resize the first index

ArrayResize(Array,Bars);

So you have

Array[Bars][0][0];

The 2nd and 3rd dimensions size are still zero

              Array[x]=value;
              Array[y]=othervalue;
              Array[z]=price;

This is the same as

              Array[0]=value;
              Array[0]=othervalue;
              Array[0]=price;

You are trying to assign values to a 3D array using only 1 dimension.

Laszlo Tormasi 2023.01.16 07:41 #2

"All I want to do is declare a 2D array with three variables stored in it."

double Array[x][y][z];

The above is not a 2d array with three variables in it.

double Array[][3];

MartinS13X 2023.01.16 08:40 #3

Keith Watford #:

This is the same as

You resize the first index

So you have

The 2nd and 3rd dimensions size are still zero

This is the same as

You are trying to assign values to a 3D array using only 1 dimension.

Well. that's embarrassing... But your answer did clarify some things.

I'm guessing this makes a lot more sense. :)

              double Array[3][1];
              ArrayInitialize (Array,0);
              ArrayResize(Array,Bars);
              
              //So how do I assign the following values to the array?
              double value = 125;            //this is bars value and has the largest amount of
              double othervalue = 2;         //this is an integer (the number of the "zigzag" at the bar value
              double price = 1.2345;         //this is the price at the bar / swing

So when I think of an array, this is what I see in my mind: (obviously without the headers)

But I'm guessing I'm wrong there...

Am I correct that if I wanted to get the value for the price at swing 4 (1.11653), I would enter:

double Price = array[2][3];

But how do I get about getting all three values?
For example, how would I get the values associated with bar number 864?

Apologies for the very n00b questions, but for some reason I'm struggling with wrapping my head around arrays.
Thanks for the help. It's much appreciated. :)

EA Buffers Not Getting Need help in a Personal indicator variable to

MartinS13X 2023.01.16 09:29 #4

So I think I just came up with the answer to my own question.

If I wanted all the values for bar 864, I would enter double array [1][];

Or can I omit the second pair of brackets?

If I just wanted all of the prices, I would use

double array [][3];

Right?

Script to calculate Average Problem with code-wont work previous value of indicator

Daniel Cioca 2023.01.16 12:54 #5

MartinS13X #:
So I think I just came up with the answer to my own question.

If I wanted all the values for bar 864, I would enter double array [1][];

Or can I omit the second pair of brackets?

If I just wanted all of the prices, I would use

double array [][3];

Right?

https://www.mql5.com/en/articles/567

MartinS13X 2023.01.16 16:59 #6

Daniel Cioca #:
https://www.mql5.com/en/articles/567

How did I not find that before??

Very helpful! Thank you.

MartinS13X 2023.01.18 10:46 #7

I have mostly solved the issues I had and think I am slowly starting to understand what happening. :)
One thing I do not understand though is how to access singular values or series of values from within the array. It's just spitting 0.0's at me.

My eventual goal is to get a range of values from the array and then perform calculations with them.
So for example, I want to get swing 3 to 7, get the associated close prices and average them.

I would expect to just go

Double Average = ((Array[3][2]+Array[4][2]+Array[5][2]+Array[6][2])/2); (or something to that end), but guessing it's not that simple.

Here's the code I have.... Hope you can give me a pointer in the right direction.

      if(NewBar()==true)
      {
      ObjectsDeleteAll(0);
         DrawSwingPoints();
            
            double ZZValue[];
            ArrayResize(ZZValue,sBars);
            
            //======================Me visualising array data=================================================
            //Array[Bars][2]
            //[0] Bars  [961]   [925]    [904]     [893]   [864]    [839]    [820]    [806]    [801]    [791]
            //[1] Swing [ 1 ]   [ 2 ]    [ 3 ]     [ 4 ]   [ 5 ]    [ 6 ]    [ 7 ]    [ 8 ]    [ 9 ]    [ 10]
            //[2] Price[1.116][1.11685][1.11628][1.11653][1.11612][1.11644][1.11624][1.11671][1.11652][1.11666]
            //=============================================================
              
              double SwingArray[][3];    //[Bars][SwingNr][Price]
              ArrayInitialize (SwingArray,0);
              ArrayResize(SwingArray,sBars);
               
         //for( int i = 0; i<Bars; i++)   //FROM MOST RECENT BAR TO OLDEST
         for( int i = Bars-1; i>0; i--)   //FROM OLDEST BAR/SWING TO LATEST
         {
               double ZigZag=iCustom(Symbol(),_Period,"ZigZag",ExtDepth,ExtDeviation,ExtBackstep,0,i);
               if(ZigZag !=0)
               {
               int x; //y, z;
               BarNr = i;
               SwingNr++;
               ZZValue[SwingNr] = ZigZag;

                  SwingArray[x][0] = BarNr;     //integer (bar number)
                  SwingArray[x][1] = SwingNr;   //integer (basically also bar number)
                  SwingArray[x][2] = ZigZag;    //This is a double (price value)
                  //ArraySort(SwingArray,WHOLE_ARRAY,0,MODE_DESCEND);                  //Arraysort does not seem to have the desired effect. 
               
                  //Print("BarNr - "+BarNr+" SwingNr - "+SwingNr+" --- "+ZZValue[SwingNr]);  //Returns all 3 numbers as advertised
                  //Print(SwingArray[x][0]);       //returns bar numbers
                  //Print(SwingArray[x][1]);       //returns swing numbers
                  //Print(SwingArray[x][2]);       //returns price
                  //Print(SwingArray[0][0]);                               //Returns all PRICES?? Only 1 Bar number (961) expected? Why do I get all of them?
                  //Print(SwingArray[0][1]);                               //Returns all swing numbers. Again, Why all of them?
                  //Print(SwingArray[0][2]);                               //Returns all prices. ... and again... why all of them? (1.116 expected)
                  //Print(SwingArray[1][0]);         //Returns all 0.0     //From here on out, no matter what combination I use. All 0.0 values.
                  //Print(SwingArray[1][1]);         //Returns all 0.0      
                  //Print(SwingArray[1][2]);         //Returns all 0.0
                  //Print(SwingArray[2][0]);         //Returns all 0.0
                  //Print(SwingArray[2][1]);         //Returns all 0.0
                  //Print(SwingArray[2][2]);         //Retunrs all 0.0

EA Codeing i get Use/return a integer value adding to array

Laszlo Tormasi 2023.01.18 12:17 #8

MartinS13X #:
I have mostly solved the issues I had and think I am slowly starting to understand what happening. :)
One thing I do not understand though is how to access singular values or series of values from within the array. It's just spitting 0.0's at me.

My eventual goal is to get a range of values from the array and then perform calculations with them.
So for example, I want to get swing 3 to 7, get the associated close prices and average them.

I would expect to just go

Double Average = ((Array[3][2]+Array[4][2]+Array[5][2]+Array[6][2])/2); (or something to that end), but guessing it's not that simple.

Here's the code I have.... Hope you can give me a pointer in the right direction.

You use variable "x" as the array index but no value is assigned to it.

               int x; //y, z;
               BarNr = i;
               SwingNr++;
               ZZValue[SwingNr] = ZigZag;

                  SwingArray[x][0] = BarNr;     //integer (bar number)
                  SwingArray[x][1] = SwingNr;   //integer (basically also bar number)
                  SwingArray[x][2] = ZigZag;    //This is a double (price value)

William Roeder 2023.01.18 12:50 #9

           //Array[Bars][2]
            //[0] Bars  [961]   [925]    [904]     [893]   [864]    [839]    [820]    [806]    [801]    [791]
            //[1] Swing [ 1 ]   [ 2 ]    [ 3 ]     [ 4 ]   [ 5 ]    [ 6 ]    [ 7 ]    [ 8 ]    [ 9 ]    [ 10]
            //[2] Price[1.116][1.11685][1.11628][1.11653][1.11612][1.11644][1.11624][1.11671][1.11652][1.11666]

First thing you must do is decide what your search value or index value is, versus what you are storing.

Ignoring bar index for now, your index value is swing and you are storing price. That would be a one-dimensional array, not two dimensions. You use swing index in and get price out.

In your case, you still use swing index in and get either bar or price out. Therefor, you need a two-dimensional array, not three. The first index is swing index, and the second selects price or bar index out.

I wouldn't use that, as you have two different data types. I would create a single dimension array of a structure of what you are actually storing.

struct Data{ int iBar; double price };
Data ZZvalue[];

   ArrayResize(ZZvalue,SwingNr+1);
      ZZvalue[SwingNr].price = ZigZag;
      ZZvalue[SwingNr].iBar  = i;
   SwingNr++;

MartinS13X 2023.01.21 21:07 #10

Laszlo Tormasi #:

You use variable "x" as the array index but no value is assigned to it.

It's easy to overlook stuff isn't it? Especially when tired and have been looking at the screen for way too long.

Thanks. :)

I'll see if I continue with this "version" or try William Roeder's suggestion, which look like it will simplify things a bit. (once I get my head around structures)

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