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Two Dimensional Array vs One Dimensional Array

  • #1
  • First Post: Aug 29, 2009 5:49am Aug 29, 2009 5:49am
Can anyone explain to me what a two dimensional array is, versus a one dimensional array and how you would go about implementing it? I understand a one dimensional array has a maximum of 50 elements and would look like so: double my_array[50]. Now, if I were to add a second dimension, does it become a multiplier of the first which, if it too contained a maximum of 50 elements, does that mean it now has a maximum of 2500 (50 x 50) elements? What I need is an array with at least 250 elements and a one dimensional array by itself I'm afraid won't work. I suspect this might be correct, so I guess all I have to do now is try to implement it.

This is what I intend to do. Does it look right?

PHP Code
for(int i=0; i<=49; i++)
  {
   for(int ii=0; ii<=49; ii++)
    {
     if(Ask=Targ[i][ii])
      { 
       Tk_1[i][ii]=OrderSend(Symbol1,OP_BUY,Lots1,Ask,Slip1,0,0,"",0,0,Lime);
       Gate1[i][ii]=1; Gate0[i][ii]=1;
      }
    }
  }
Thanks in advance.
  • #2
  • Aug 29, 2009 6:01am Aug 29, 2009 6:01am
Of course this doesn't tell anything about how to assign the variables. I suppose that would help too.
  • #3
  • Edited 8:29am Aug 29, 2009 8:10am | Edited 8:29am
Okay, apparently I seem to have the right idea.

This is what I did to load the array:

PHP Code
double Targ1[50][5]; Tier1=Point*8; Tier2=Tier1*5;

for(int a=0; a<=49; a++)
  {
   for(int b=0; b<=4; b++)
     {
      Targ1[a][b]=TB_Hi-(Tier2*a)-(Tier1*b);
     }
   }
However, I am having the same problem as I did with a single dimension array.

This is essentially what I did to create it:

PHP Code
double Targ1[50],Targ2[50],Targ3[50],Targ4[50],Targ5[50];
Tier1=Point*8; Tier2=Tier1*5;

for(int a=0; a<=49; a++)
  {
   Targ1[a]=TB_Hi-Tier2*a;    Targ2[a]=Targ1[a]-Tier1*1;
   Targ3[a]=Targ1[a]-Tier1*2; Targ4[a]=Targ1[a]-Tier1*3;
   Targ5[a]=Targ1[a]-Tier1*4;
  }
So, instead of creating a two dimensional array with one "tier" every 40 points, and dividing it into 5 sub-tiers, where each sub-tier is 8 points, I created 5 separate one dimensional "mini" arrays which, when staggered every 8 points, comes out to 40 points. So, they effectively do the same thing.

The only problem is when I go to plot the coordinates on the grid (in both cases), it's missing every 5th element and is messing me up. Actually, it doesn't work too bad the way it is, except I'm trying to implement something else, which is contingent upon all "5 cylinders" firing, so to speak.

Now I did manage to get it to work, although it's a bit unorthodox (by setting the target past the middle of each tier, instead of at the beginning or the end), except I was wondering if there was a more formal way of going about it?

In the first case it would look like this:

PHP Code
double Targ1[50][5]; Tier1=Point*8; Tier2=Tier1*5;

for(int a=0; a<=49; a++)
  {
   for(int b=0; b<=4; b++)
     {
      Targ1[a][b]=TB_Hi-(Tier2*a)-(Tier1*b)-Point*7; // added -Point*7
     }
   }
Anyone got any ideas?

Thanks!
  • #4
  • Aug 29, 2009 11:32am Aug 29, 2009 11:32am
hey ec..... not sure how your arriving at a maximum of 50..... also not sure what your trying to accomplish..... but here are some thoughts......

single arrays can be thought of as 1 liners..... such as Close[], Open[] and such....

double arrays can be thought of as a checker board.....

int board[8][8]; here the number of elements is set.....

so if some said board[3,6] , you should know exactly which square he was speaking of..... and if he said board[3,9], you'd know he had know clue as to what he was talkin about.....

three deminsional arrays can be thought of as a rubicks cube.....

int cube[3][3][3];

so if someone said cube[2,0,1] you can again, know exactly the destination/address/data.....

//------

all that aside, a single array can hold many elements..... it could most likely handle your task......h
to trade and code, keep both simple... no call to impress....h
  • #5
  • Edited Aug 30, 2009 1:00am Aug 29, 2009 2:14pm | Edited Aug 30, 2009 1:00am
Quoting hayseed
hey ec..... not sure how your arriving at a maximum of 50..... also not sure what your trying to accomplish..... but here are some thoughts......

single arrays can be thought of as 1 liners........
Wow! Yeah, I see what you're saying. So, I was essentially correct when saying if I had a two dimensional array "set" at 50 in each dimension, it would yield 2500 (i.e., 50 x 50) elements. Or, if it were a three dimensional array, it would yield 125,000.

As far as the maximum number of elements is concerned, apparently I must have misunderstood when reading about it awhile back.

This was the only place I could find it referenced in the MQL4 Reference under Array functions:

Quote
A group of functions to work with arrays.

Arrays are allowed to be maximum four-dimensional. Each dimension is indexed from 0 to dimension size-1. In a particular case of a one-dimensional array of 50 elements, calling of the first element will appear as array[0], of the last one - as array[49].
So yes, it looks like they are just giving this as an example, and not specifying a maximum. So this is good to know!

Hey, Thanks!
  • #6
  • Aug 29, 2009 2:24pm Aug 29, 2009 2:24pm
hey ec..... yes, that is my belief also.....h
to trade and code, keep both simple... no call to impress....h
  • #7
  • Aug 30, 2009 1:19am Aug 30, 2009 1:19am
Okay, having said that, I created a new one dimensional array with 250 elements and plotted them at 8 point intervals on the grid, and I'm still having the same problem. It's skipping every 5th interval and not plotting it on the grid. Which would be understandable (or at least give me some idea why) if I were creating 5 arrays and stacking them like I before but, now I'm not. So I looked at the code and made sure there was no longer any references to the number 5 (I used it as a multiplier twice previously) suspecting it was somehow related to the cause, but nope, it's still does the exact same thing. Weird!
  • #8
  • Aug 30, 2009 11:07am Aug 30, 2009 11:07am
what exactly are you trying to do..... h
to trade and code, keep both simple... no call to impress....h
  • #9
  • Aug 30, 2009 12:52pm Aug 30, 2009 12:52pm
I am trying to plot a grid system, which places a trade every so many points (currently it's set at 8). But like I said, it's missing or not placing a trade at every 5th interval. And it doesn't seem to matter how I go about doing it, whether it's 5 separate arrays, that are stacked and contain 50 elements apiece or, whether it's a larger array containing 250 elements.
  • #10
  • Aug 31, 2009 9:25am Aug 31, 2009 9:25am
hey ec...... if your goal is to just place trades, might be simplier just to employ a loop.... this is safest done using a script, not an ea..... but it can be done in a true ea.....

are you familar with loops..... such as below.......

highly suggest scripts only..... might be errors in my code, didn't check it.....h

Inserted Code
 
#property show_inputs
 
extern bool    Trade       = false;
       int    ProfitTarget =   100;
       int    Stoploss     =   100;
       int    Slippage     =     3;
       int    grid         =    10;
       int    buylimit;
       double buylimitgrid;
 //----
       int    trades       =     5;      
       int    orders;
//+------------------------------------------------------------------+
//+------------------------------------------------------------------+
int start()
  {
//----
     orders = trades - 1;
//----
     if(Trade && OrdersTotal() < orders)
     {
     for(int i=trades;i>=0;i--)
     while(true)
     {
      buylimit   = OrderSend(Symbol(),OP_BUYLIMIT,0.01,Ask-(buylimitgrid*Point),Slippage,Ask-((Stoploss+buylimitgrid)*Point),Ask-((buylimitgrid-ProfitTarget)*Point),0,0,0,Red); 
 
      buylimitgrid = buylimitgrid+grid;
      if(buylimit<=0) Print("Error = ",GetLastError());
      else { Print("error"); break; }
      Sleep(3000);
      }
      }
 
 
 
 
 
   return(0);
   }
to trade and code, keep both simple... no call to impress....h
  • #11
  • Aug 31, 2009 10:41am Aug 31, 2009 10:41am
Aside from plotting trades, there are other things I'm trying to do with it. But, unless I can plot the trades correctly it won't work. And yes, I am using a loop, actually two, one for setting up the grid, and one for accessing it (see first three posts).

So, what's the deal with the script? Is it jut a one shot deal, where it sets up the grid places trades all day? Or can you program more functionality into it than that? Because I am trying to get it to vary lot size, modify and delete orders but, only at specific thresholds, and stuff like that. Can this be programmed into a script? I don't know, because thus far, I've only worked with EA's.
  • #12
  • Aug 31, 2009 12:24pm Aug 31, 2009 12:24pm
hey ec..... yes, scripts are a one shot deal.....

you create scripts the same manner as ea's just choose script when MetaEditor asks what you want to create.....

copy and paste the example code above and compile..... then place it on any demo chart..... most scripts do not show the inputs, on this one switch trade to true......you'll see the orders placed.....

i always use scripts for placing large number of orders..... for safety.....

yes, you can do the same thing with ea's , just need some backup code to assure nothing gets hung up......

i lost a couple grand in a few minutes once when a loop kept placing orders in a live account..... it could have been worse......h
to trade and code, keep both simple... no call to impress....h
  • #13
  • Edited Sep 1, 2009 1:45pm Aug 31, 2009 8:39pm | Edited Sep 1, 2009 1:45pm
Quoting hayseed
i lost a couple grand in a few minutes once when a loop kept placing orders in a live account..... it could have been worse......h
Ouch! ... Yes, I have had this happen to me too, except fortunately it was on a demo account. But it seemed like it was always a programming issue, and was something I could correct.

Here is an example of what I do to insure only one order is open at any particular level:

PHP Code
//---- Open Buy Order
if(Ask==Targ5[i]&&Gate5[i]==0)
   {
    Tk_5[i]=OrderSend(Symbol1,OP_BUY,Lots1,Ask,Slip1,0,0,"",0,0,Lime); Gate5[i]=1;
   }
//---- Check if Order has Closed
if(OrderSelect(Tk_5[i],SELECT_BY_TICKET,MODE_HISTORY)==true)
   {
    datetime ctmT5=OrderCloseTime(); if(ctmT5>0){ Gate5[i]=0; }
   }
And here, Gate5[i] (in accord with Targ5[i] and Tk_5[i]) is preset to "0" which, once the order is placed, is set to "1." And it will remain set to "1" (thus prohibiting any new orders) until OrderCloseTime() is queried and it's determined the order has actually closed. At which point Gate5[i] is reset to "0" and, once Targ5[i] is reached, it opens a new order.

So long as I implement something like this, I rarely seem to have any problems.
  • #14
  • Last Post: Sep 1, 2009 10:33am Sep 1, 2009 10:33am
hey ec.... actually the ea counts the orders twice to assure no mix ups.... it uses limit and stop orders in large numbers.....

it was counting the wrong type orders... so it never maxed out.....

no big deal though, huge losses are common for me and that one is no where near the record book.....

it was the dumb mistake that i gave myself a good thrashing for......h
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to trade and code, keep both simple... no call to impress....h
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