how to handle a matrix in MQL4?

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62	marshall318 2008.01.20 03:16 My Matlab function has a matrix output. If I call it from my EA, how do I deal with it ? If MQL4 can not handle it, how shall I get around it? Pls help me. Thanks

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2462	phy 2008.01.20 21:53 Are you trying to read a file output by MatLab, or making a call from MT4 to return data via DLL ?

62	marshall318 2008.01.20 23:46 phy wrote: Are you trying to read a file output by MatLab, or making a call from MT4 to return data via DLL ? I am making a call from MT4 to return data via DLL.

2462	phy 2008.01.21 03:12 If you wish to receive more than one value per call, then use an array to transfer the data.

marshall318 2008.01.23 11:23

phy wrote:

If you wish to receive more than one value per call, then use an array to transfer the data.

My matlab function is like this:

Y = Myfunc(v1,v2)

The ouput Y is a cell array {y1 y2}, y1 is a 1x1 matrix, y2 is a mxn matrix, If I call this function in MT4 via DLL, how can I get the output to MT4 environment ? thanks a lot.

2462

phy 2008.01.23 21:56

Call matlab from mt4 with one of the parameters being the address of an appropriately sized/dimensioned array storage space in which matlab can store data.

If it is two arrays, you have to return them separately (two calls from MT4).

Someone else may have a better idea.

What are you building?

marshall318 2008.01.24 06:01

phy wrote:

Call matlab from mt4 with one of the parameters being the address of an appropriately sized/dimensioned array storage space in which matlab can store data.

If it is two arrays, you have to return them separately (two calls from MT4).

Someone else may have a better idea.

What are you building?

I am building NNs in Matlab. I still don't have a clue how it works, two calls from MT4? why does each call return one output while the function does have two outputs? thanks

2462

phy 2008.01.24 06:31

My understanding:

You can return a single value to MT4 via an external call.

Or, you can give MatLab the starting address of an MT4 array to fill with data.

I'm not quite expert on this, so I could be wrong, but, the options are limited.

Here are the MT4 side definitions from the SampleDLL

#import "ExpertSample.dll"
int    GetIntValue(int);
double GetDoubleValue(double);
string GetStringValue(string);
double GetArrayItemValue(double arr[],int,int);
bool   SetArrayItemValue(double& arr[],int,int,double);
double GetRatesItemValue(double rates[][6],int,int,int);
int    SortStringArray(string& arr[],int);
int    ProcessStringArray(string& arr[],int);

No complex types are returned, but...

bool   SetArrayItemValue(double& arr[],int,int,double);

This sample call gives the address of an array to the external code which it can manipulate, as an example of you "returning" a matrix. Note it
does not "return" an array, but the array is accessible to both the DLL and MT4.
 
If you have to fill two arrays, you could hand over two array addresses ( ok, two calls not required )
 
double array1[100];
double array2[100][10];
 
Call to DLL/MatLab:
FillMyArrays( double &array1[], double  &array2[][]);
 
 
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Other references
 
'Interaction between MetaTrader 4 and Matlab via CSV Files'
 
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You might even post your question on the Russian side of this forum, it seems to be inhabited by more experienced programmers.

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how to handle a matrix in MQL4?