How to sort an array? | Forex Factory

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How to sort an array?

  • #1
  • First Post: May 18, 2012 9:27am May 18, 2012 9:27am
The following code was taken from Forex Robot developed by Dietcoke , this part of the EA deals with establishing an array list of pairs of interest

void CreateSymbolList()
{
int hFileName = FileOpenHistory("symbols.raw",FILE_BIN|FILE_READ);
int Records = FileSize(hFileName) / 1936;
int Counter = 0;
for(int i = 0; i < Records; i++)
{
string TempSymbol = StringTrimLeft(StringTrimRight(FileReadString(hFileName,12)));
if(MarketInfo(TempSymbol,MODE_BID) > 0 && PairAllowed(TempSymbol))
{
if( StringFind(Ignore.Pair,TempSymbol,0) < 0 && IndexAllowed(TempSymbol) )
{
ArrayResize(Pairs,Counter+1);
Pairs[Counter] = TempSymbol;
if(TempSymbol == Symbol()) ThisSymbolIndex = Counter;
//log("ThisSymbolIndex",ThisSymbolIndex,Pairs[ThisSymbolIndex]);
//log("CreateSymbolList: Counter=",Counter,TempSymbol,Symbol());
Counter++;
}
}
FileSeek(hFileName,1924,SEEK_CUR);
}
FileClose(hFileName);
return(0);
}


But lets say we want to introduce a RSI daily 20 period progesssion and we wanted to rank the pairs not alphabetically as above, but by RSI decending values - NOW How would I do that ???
  • #2
  • May 18, 2012 3:17pm May 18, 2012 3:17pm
ArraySort()
  • #3
  • May 19, 2012 5:15am May 19, 2012 5:15am
Quoting CodeMeister
ArraySort()
Of course it's an ArraySort () function but applied in what way ?
  • #4
  • May 19, 2012 5:28am May 19, 2012 5:28am
Quoting lucklogic
Of course it's an ArraySort () function but applied in what way ?
My guess is you're not a programmer.
  • #5
  • May 19, 2012 7:34am May 19, 2012 7:34am
Why don't you just use a 2 dimension array with the relevant RSI data in the first dimension and the pair data in the second and then use the ArraySort() ??
If you think I'm mad, I must be mad
  • #6
  • May 19, 2012 9:29am May 19, 2012 9:29am
Quoting cyber1
My guess is you're not a programmer.
I'm an amateur but I can get by, but that's the point of this thread, isn't it
  • #7
  • May 19, 2012 9:35am May 19, 2012 9:35am
Quoting futurespec
Why don't you just use a 2 dimension array with the relevant RSI data in the first dimension and the pair data in the second and then use the ArraySort() ??
So like ; double SortRSI[1][21]; // where 21 is number of pairs and 1 is the RSI that I want to collect
  • #8
  • May 19, 2012 10:03am May 19, 2012 10:03am
Think it is more likely to be [21][1]
If you think I'm mad, I must be mad
  • #9
  • May 19, 2012 10:37am May 19, 2012 10:37am
[quote=lucklogic;5680677]The following code was taken from Forex Robot developed by Dietcoke , this part of the EA deals with establishing an array list of pairs of interest

void CreateSymbolList()
{
int hFileName = FileOpenHistory("symbols.raw",FILE_BIN|FILE_READ);
int Records = FileSize(hFileName) / 1936;
int Counter = 0;
for(int i = 0; i < Records; i++)
{
string TempSymbol = StringTrimLeft(StringTrimRight(FileReadString(hFileName,12)));
if(MarketInfo(TempSymbol,MODE_BID) > 0 && PairAllowed(TempSymbol))
{
if( StringFind(Ignore.Pair,TempSymbol,0) < 0 && IndexAllowed(TempSymbol) )
{
ArrayResize(Pairs,Counter+1);
Pairs[Counter] = TempSymbol;
if(TempSymbol == Symbol()) ThisSymbolIndex = Counter;
//log("ThisSymbolIndex",ThisSymbolIndex,Pairs[ThisSymbolIndex]);
//log("CreateSymbolList: Counter=",Counter,TempSymbol,Symbol());
Counter++;
}
}
FileSeek(hFileName,1924,SEEK_CUR);
}
FileClose(hFileName);
return(0);
}


So it may be best to leave the above function as it is, that creates the Pairs list, and start a new function to add RSI and sorting eg:

double SortRSI[21][1];
int NoToPrint =0;

DeleteObjects();

for (int cc = 0; cc < NoOfPairs; cc++) // NoOfPairs previously calculated
{

int rsi = iRSI(TradePair[cc], PERIOD_D1, 20, 0, 0);

SortRSI[NoToPrint][0] = rsi;
NoToPrint++;



// and then

ArraySort(SortRSI,NoToPrint,0,MODE_DESCEND);

for (int cc2 = 0; cc2 < NoToPrint; cc2++)
{
cc = SortRSI[cc2][1];


rsi = SortRSI[cc2][0];

DisplayLine(cc2,TradePair[cc], rsi);

}
} //for (int cc = 0; cc <= NoOfPairs; cc++)


Is that about right ???
  • #10
  • Edited 3:57am May 20, 2012 3:42am | Edited 3:57am
Too early for me to get my head around this! Always have to think a bit when dealing with arrays, I would just code it / try it/ amend as necessary.

BUT 1 way ..........

String mRsiData[NoOfPairs], mPair;

for (int cc = 0; cc < NoOfPairs; cc++) // NoOfPairs previously calculated
{

double rsi = iRSI(TradePair[cc], PERIOD_D1, 20, 0, 0); // double
mRsiData[cc]= (DoubleToStr(rsi, Digits) + Pairs[cc]);
} // need to populate the array first!

ArraySort(mRsiData, WHOLE_ARRAY, 0, MODE_ DESCEND);

for (int z = 0; z < NoToPrint; z++) // If 'NoToPrin't is array size
{

rsi = StringSubstr(mRsiData[z], 0, StringLen(mRsiData[z]) - 6);
mPair = StringSubstr(mRsiData[z], StringLen(mRsiData[z]) - 6, 6)
DisplayLine(z, mPair , rsi);

}

Not elegeant but hopefully will work. Sorry but cannot think about arrays at moment.... especially when you want to mix strings and doubles.

HTH

EDIT : Sorry 'rsi' used in 2 places...
change to
String String_rsi = StringSubstr(mRsiData[z], 0, StringLen(mRsiData[z]) - 6);
mPair = StringSubstr(mRsiData[z], StringLen(mRsiData[z]) - 6, 6)
double mRsi = StrToDouble(String_rsi);
DisplayLine(z, mPair , mRsi);

Now that is untidy but you should get the idea
If you think I'm mad, I must be mad
  • #11
  • May 20, 2012 11:41pm May 20, 2012 11:41pm
Quoting lucklogic
I'm an amateur but I can get by, but that's the point of this thread, isn't it
//----

hey luck...... the trouble is, occasionally someone asks for something rare..... there are very very few indicators or experts with strings and doubles sorted so as to correctly rank them in order side by side..... there is a reason for that rarity......

the few that exist are often private or ex file....... can't recall ever seeing 'the code' of one public......

//-----

did you try futurespec's suggestion......

did it work for you.....

if not, and your still interested in it, holler back..... i'll post somethin rare....... all us amatuers gotta stick together......h
to trade and code, keep both simple... no call to impress....h
  • #12
  • May 21, 2012 5:32am May 21, 2012 5:32am
I could not get either method to work on the pairs that I was interested in, from my first posting.

However I have attached a fully working indicator that does indeed successfully mix (string) pairs and (double) ranking system (TMA Slope)

It would still be nice to apply this to the first posting but I cannot see the way when the pairs are generated via that method, this implies that the pair
pre-processing is the key part
Attached File(s)
File Type: mq4 TMASlope display 4hrs.mq4   9 KB | 560 downloads
  • #13
  • May 21, 2012 6:08am May 21, 2012 6:08am
As far as I understand, ArraySort() only works on the first dimension, so that
[1.234][0]
[1.456][1]
would change into
[1.456][0]
[1.234][1]
...didn't check that

I would work with two identical arrays (same content) with dimensions [#of pairs][2] for the rsi/pair index combination ([x][0] would contain the rsi value and [x][1] the pointer into your pair array->myarray[0][0]=rsi; myarray[0][1]=pointer) and sort one of them with ArraySort()

next step would be to run through the sorted array and search for the corresponding value in the second (unsorted) array
so you get the first value as 1.456 and look in the second array what the original pair pointer was and replace it in the sorted array
  • #14
  • May 21, 2012 8:29am May 21, 2012 8:29am
hey luck..... wasn't aware of that indicator.... it should accomplish your goals......

rather than adding another function, wouldn't it be easier to just enter the desired pairs in the inputs....h
to trade and code, keep both simple... no call to impress....h
  • #15
  • May 21, 2012 8:41am May 21, 2012 8:41am
Quoting hayseed
hey luck..... wasn't aware of that indicator.... it should accomplish your goals......

rather than adding another function, wouldn't it be easier to just enter the desired pairs in the inputs....h

Yes that's right and as an indicator it works great but I wanted to use the pair ranking / sorting idea in the context of an EA that is coded as per my first post.

I could try and recode my first post into the fashion of the indicator that works but that's a job that's likely to be beyond my understanding of the code and the way it works
  • #16
  • May 21, 2012 8:43am May 21, 2012 8:43am
Quoting iwjw
As far as I understand, ArraySort() only works on the first dimension, so that
[1.234][0]
[1.456][1]
would change into
[1.456][0]
[1.234][1]
...didn't check that

I would work with two identical arrays (same content) with dimensions [#of pairs][2] for the rsi/pair index combination ([x][0] would contain the rsi value and [x][1] the pointer into your pair array->myarray[0][0]=rsi; myarray[0][1]=pointer) and sort one of them with ArraySort()

next step would be to run through the sorted array and search for the corresponding value in the...

A two dimensional array is used - see attached indicator
eg, double SortRSI[21][6];
  • #17
  • May 21, 2012 9:01am May 21, 2012 9:01am
Quoting lucklogic
Yes that's right and as an indicator it works great but I wanted to use the pair ranking / sorting idea in the context of an EA that is coded as per my first post.

I could try and recode my first post into the fashion of the indicator that works but that's a job that's likely to be beyond my understanding of the code and the way it works

//---

hey luck..... it's difficult for us to take bits and pieces of code and merge them together with out seeing the entire code of everything involved.... there are too many unknowns......

i'll post somethin later.....h
to trade and code, keep both simple... no call to impress....h
  • #18
  • May 21, 2012 9:52am May 21, 2012 9:52am
Quoting hayseed
//---

hey luck..... it's difficult for us to take bits and pieces of code and merge them together with out seeing the entire code of everything involved.... there are too many unknowns......

i'll post somethin later.....h

I have attached the entire EA for your amusement but the relevant bit is in my first post

This is a active EA in development but I think it needs to go in a different direction - hence my request for assistance
Attached File(s)
File Type: mq4 Forex Robot-v6.23_2.mq4   46 KB | 555 downloads
  • #19
  • Edited 4:40am May 23, 2012 4:28am | Edited 4:40am
[/quote] Hayseed



if not, and your still interested in it, holler back..... i'll post somethin rare....... all us amatuers gotta stick together......h[/quote]



I'll like to have your input
  • #20
  • Edited 1:08am May 24, 2012 12:27am | Edited 1:08am
Quoting lucklogic
But lets say we want to introduce a RSI daily 20 period progesssion and we wanted to rank the pairs not alphabetically as above, but by RSI decending values - NOW How would I do that ???
Lucklogic,

Good question. Assuming that I've understood you correctly.........

If I have to sort multiple items, I build a string that consists of: sort key, item1, item2, item3, etc.

However, you can't use MQL4's ArraySort() to sort string arrays. I've added more than 70 new functions to the MQL4 language, which I've shared freely here. Among these are array sort functions, and number-to-string and string-to-number formatting functions.

RSI is always a positive number between 0 and 100, which makes things easy; item1 (RSI) and item2 (pair symbol) can be incorporated in, and extracted from, the sort key. Hence I would build a string array from the RSI and pair symbol arrays, that consists of NumberToStr(RSI) and then the pair symbol. Then I'd simply use my own ShellsortStringArray() function to sort the array into descending sequence, and then finally deconstruct the string to extract the items.

Here is a sample script:
Inserted Code
//+------------------------------------------------------------------+
//|                                                            x.mq4 |
//+------------------------------------------------------------------+

#include <[color=Green]hanover --- function header.mqh[/color]>

//+------------------------------------------------------------------+
int start()   {
//+------------------------------------------------------------------+

[color=Blue]  [color=Gray]// load sample arrays with 10 pair symbol IDs, and 10 corresponding RSI values.......[/color]
[/color]  string pair_symbol[10] = {"EURUSD","USDCAD","NZDJPY","GBPJPY","GBPCHF","AUDUSD","USDJPY","USDCHF","EURAUD","AUDCAD"};
  double RSI_value[10]   = {46,10,55,79,28,93,12,66,51,8};
  
[color=Blue]  [color=Gray]// build sort array: first 3 characters are the RSI, then the corresponding pair symbol......[/color]
[/color]  string array_for_sorting[10];
  for (int i=0; i<ArraySize(pair_symbol); i++)
    array_for_sorting[i] = [color=Green]NumberToStr(RSI_value[i],"Z3")[/color] + pair_symbol[i];  [color=Gray]// "Z3" right aligns RSI to 3 characters with leading zeros, then append symbol[/color]

  [color=Blue][color=Gray] // perform the sort.......  [/color]
[/color]  [color=Green]ShellsortStringArray(array_for_sorting,true);[/color]   [color=Gray]// true sorts in descending order[/color]

[color=Blue] [color=Gray]  // now deconstruct the sorted values back to the original arrays...... [/color] 
[/color]  for (i=0; i<ArraySize(pair_symbol); i++)  {
    pair_symbol[i] = StringSubstr(array_for_sorting[i],3);                   [color=Gray]// pair is stored in position 3 onward[/color]
    RSI_value[i]   = StrToDouble(StringSubstr(array_for_sorting[i],0,3));    [color=Gray]// RSI is stored in character positions 0 thru 2[/color]
  }
  
[color=Blue]  [color=Gray]// display the result......[/color]
[/color]  MessageBox([color=Green]StringArrayToStr(pair_symbol,"T6")[/color] + "\n" + [color=Green]DoubleArrayToStr(RSI_value,"T3")[/color]);
  return(0);
}
//+------------------------------------------------------------------+

#include <[color=Green]hanover --- extensible functions.mqh[/color]>
In the result, you can see how the RSI values are in descending order, with their pair symbols in the corresponding elements:
AUDUSD,GBPJPY,USDCHF,NZDJPY,EURAUD,EURUSD,GBPCHF,USDJPY,USDCAD,AUDCAD
93,79,66,55,51,46,28,12,10,8

The elements in the array_to_sort[] array look like this:
093AUDUSD,079GBPJPY,066USDCHF,055NZDJPY,051EURAUD,046EURUSD,028GBPCHF,012USDJPY,010USDCAD,008AUDCAD

I "cheated" by using some of my own functions — I have highlighted these in green typeface. But everything else is straight-up MQL4. The entire "construct—sort—deconstruct" process requires only 8 lines of code.

Anyway, that is how I would approach your question. Hope it gives you some ideas to work with.

Good luck,
David

[EDIT] Forgot to mention: you need to copy the attached files into your ..../experts/include folder.
Attached File(s)
File Type: mqh hanover --- function header.mqh   11 KB | 516 downloads
File Type: mqh hanover --- extensible functions.mqh   89 KB | 536 downloads
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