How to draw the difference between two moving averages as a histogram on H1 time frame in MQL4? - algorithmic-trading

Question

This is my trial to draw the difference between two moving averages as a histogram on H1 time frame. The problem is that it does not change when I change a time frame, especially to lower ones. I am a beginner at MQL4, with no experience or programming background, so please explain to me the mistake.
#property indicator_separate_window
#property indicator_buffers 1
#property indicator_color1 Gray
#property indicator_width1 2
extern int maperiod1 = 25;
extern int maperiod2 = 55;
extern int timefr = 60;
double mainbuffer[];
int init(){
SetIndexBuffer( 0, mainbuffer );
SetIndexStyle( 0, DRAW_HISTOGRAM );
return(0);
}
int start(){
int counted_bars = IndicatorCounted();
if ( counted_bars < 0) return(-1);
if ( counted_bars > 0) return( 0);
int limit = ( Bars - counted_bars );
for ( int i = limit; i >= 0; i-- ){
int shift = iBarShift( NULL, timefr, Time[i] );
double maB = iMA( NULL, timefr, maperiod1, 0, MODE_EMA, 0, shift );
double maR = iMA( NULL, timefr, maperiod2, 0, MODE_EMA, 0, shift );
mainbuffer[shift]= ( maB - maR );
}
return(0);
}

Answer 1

In your code you calculate MA of H1 timeframe, that is why there's no difference what happens on smaller timeframes - it checks H1 only.
if (counted_bars>0) return(0);
- as far as i can remember, if number of counted bars if positive, you need to decrease it by one in order to recalculate previously known bar: if (counted_bars>0) counted_bars--;

Answer 2

Besides the "immunity" to any TimeFrame selection,the code does not provide means to update in sync with Time[] properly
As Daniel has already noted above the "rigid", hard-coded relation to an extern pre-selected time-frame ( which technically ought be designed as rather some enum:
enum ENUM_GUI_SELECT_TFRAME {
M1 = PERIOD_M1,
M5 = PERIOD_M5,
...
..
.
H1 = PERIOD_H1,
H4 = PERIOD_H4,
...
..
.
MN = PERIOD_MN
};
// ++++------------------------------------------ MAKES SURE,
// |||| ALWAYS ONLY
// |||| PROPER VALUES GET
// vvvv EVER SELECTED
extern ENUM_GUI_SELECT_TFRAME timefr = PERIOD_H1;
) there are some further points to solve with code-activation / execution barriers.
What prevents the code from proper updates?
This tandem of conditions:
if ( counted_bars < 0) return(-1);
if ( counted_bars > 0) return( 0);
is met if and only if the IndicatorCounted() == 0, never more.
IndicatorCounted() ~ The function returns the amount of bars not changed after the indicator had been launched last.
So the Custom Indicator works as a devil during the first call, where there were all bars "changed" since the ( non-existent ) previous call. After that, until a newly created bar, the Indicator gets called with having passed the condition because the IndicatorCounted() == 0, but no new bars have yet appeared -- which would thus make the IndicatorCounted() == 1 and the rest of the code of the Custom Indicator will not get executed -- which seems rather the very mirrored logic, the Custom Indicators were equipped with to avoid non-productive loops in case no new bars were created, but to get an immediate update in case a new bar has started.
In other words, even in case the IndicatorCounted() == 0 the last ( hot ) value [0] could still and does change, so if and only if the Custom Indicator value is somehow dependent on this actual ( still changing ) live-value of Close[0], it makes due sense to update the [0] cell of the mainbuffer[].
If it is not dependent on Close[0], it makes no sense to run the code, as it would not update anything.