External variable or Extern Variable MQL4
From Last Chapter
Extern ones also determine the input parameters of an mql4 EA
They are available from the Properties window
Extern variables can be modified in the Properties window and MQL4 Program
This chapter we would talk about how to coding EA properties
Learn to know Moving Average Indicators
Learn to know Moving Average Functions
Function Name
double iMA
Function Parameter
Function Value
Function Value Name
Function Meaning
symbol
NULL
ENUM_TIMEFRAMES
0
PERIOD_CURRENT
1
PERIOD_M1
5
PERIOD_M5
15
PERIOD_M15
30
PERIOD_M30
60
PERIOD_H1
240
PERIOD_H4
1440
PERIOD_D1
10080
PERIOD_W1
43200
PERIOD_MN1
ma_period
Averaging period for calculation
MA shift
Indicators line offset relate to the chart by timeframe
ENUM_MA_METHOD
0
MODE_SMA
1
MODE_EMA
2
MODE_SMMA
3
MODE_LWMA
ENUM_APPLIED_PRICE
applied_price 0
PRICE_CLOSE
Close price
applied_price 1
PRICE_OPEN
Open price
applied_price 2
PRICE_HIGH
The maximum price for the period
applied_price 3
PRICE_LOW
The minimum price for the period
applied_price 4
PRICE_MEDIAN
Median price, (high + low)/2
applied_price 5
PRICE_TYPICAL
Typical price, (high + low + close)/3
applied_price 6
PRICE_WEIGHTED
Weighted close price, (high + low + close + close)/4
shift
Current candle is 0 (candle 1-N is count back from current candle)
iMA Function Moving Average from MetaQuotes Example
iMA Function Moving Average in MetaQuotes EA or Expert Advisor Examples have 2 lines use iMA function
that's
ma=iMA(NULL,0,MovingPeriod,MovingShift,MODE_SMA,PRICE_CLOSE,0);
This we would learning how to build EA properties for this function
Basic variable Data Type
Every Vaiable should contain and specific data type as below
int (integers)
double (real numbers)
bool (Boolean values, that is logical values)
string (values of string type)
color (values of color type)
datetime (values of date and time)
Extern MQL4 Variable Group
1. Input Value directly (Like input to Edit Box) to the MQL4 EA properties
2. Input Value pass Boolean drop down list to the MQL4 EA properties
3. Input Value pass EA Methode Function
Time to change the properties of MetaQuotes EA or Expert Advisor Examples code
Function from original code
ma=iMA(NULL,0,MovingPeriod,MovingShift,MODE_SMA,PRICE_CLOSE,0);
This we would add 3 lines to select Time Frame, Moving Everage and Apply Price, so add code as below to EA properties
Input Enum Variable to the Moving Average Function to the MQL4 code
We have 3 enum variable now
TimeFrameUsed
EMA_method1
Applied_Price1
from original iMA function in the code
ma=iMA(NULL,0,MovingPeriod,MovingShift,MODE_SMA,PRICE_CLOSE,0);
Change to
ma=iMA(NULL,TimeFrameUsed,MovingPeriod,MovingShift,EMA_method1,Applied_Price1,0);
Test Run Moving Average EA on youtube
VIDEO