How to notify a number increase & decrease in MQL4 code? - mql4

Question

can anyone help me, how to write MQL4 code to know if the result is increase OR decrease..
Example:
if a result was first 0.0543 and then it is increased to 0.1342 and later decreased to 0.10345, I want to implement it to my code below:
int start()
{
double val = iCustom( NULL, 0, "SS2009_B", 0, 0, 0 );
ObjectSet( "TimeLable11", OBJPROP_CORNER, obCorner );
ObjectSetText( "TimeLable11", "Result : " + val,
fsize,
"Microsoft Sans Serif",
Yellow
);
return( 0 );
}
I want the result to have an increasing OR a decreasing notification.
Example :
Result : 0.1849 Increasing
Result : 0.01324 Decreasing

Answer 1

To have a SIMPLE example:
//------------------------------------------------------------------
#property copyright "Copyright 2015"
//------------------------------------------------------------------
// Standard Variables (define a variable to store previous value)
//------------------------------------------------------------------
double viIndicatorValuePrev = 0.0000;
int start() {
double viIndicatorValueNow = iCustom(NULL,0,"SS2009_B",0,0,0);
//------------------------------------------------
//Decide on direction (increasing or decreasing)
//------------------------------------------------
string vsDirection = "Same";
if( viIndicatorValueNow>viIndicatorValuePrev)
vsDirection = "Increasing";
if( viIndicatorValueNow<viIndicatorValuePrev)
vsDirection = "Decreasing";
//------------------------------------------------
//------------------------------------------------
// Do your thing here (ie, display stuff)
//------------------------------------------------
ObjectSet( "TimeLable11", OBJPROP_CORNER, obCorner);
ObjectSetText(
"TimeLable11"
, "Result : " + viIndicatorValueNow + " (" + vsDirection + ")"
, fsize, "Microsoft Sans Serif", Yellow
);
//------------------------------------------------
// Store current value for future comparison
//------------------------------------------------
viIndicatorValuePrev = viIndicatorValueNow;
//------------------------------------------------
return(0);
}
Hope this example helps.

Answer 2

Solution to monitor & show delta per each aMarketEVENT call of start() ( upon aMarketQUOTE aka Tick arrival )
First you need a method to store and retain a value, that becomes "old", in the meantime, before the start() ( well actually an OnTick() in the new-MQL century ) is called next time.
A static double is a smart way to go:
static double previousVALUE = EMPTY; // initialised to EMPTY
Next, initialise it in accord with a forward-stepping logic of the Custom Indicator "SS2009_B"
if ( previousVALUE == EMPTY ) {
previousVALUE = iCustom( NULL, // a Symbol
0, // a TimeFRAME
"SS2009_B",
0,
0, // a Buffer# to get value from
1 // step-back one Bar
);
}
For syntax details, review MQL4 documentation
double iCustom(
string symbol, // symbol
int timeframe, // timeframe
string name, // path/name of the custom indicator compiled program
... // custom indicator input parameterA (if
... // custom indicator input parameterB (if
... // custom indicator input parameterC (if necessary)
int mode, // line index
int shift // shift
);
Finally calculate delta & show it on UI & shuffle to get ready for a next call
double currentVALUE = iCustom( NULL, 0, "SS2009_B", 0, 0, 0);
double deltaVALUE = previousVALUE - currentVALUE;
previousVALUE = currentVALUE; // shuffle [1]<-[0] before RET/next call
if ( deltaVALUE > 0 ){
ObjectSetText( "TimeLabel11",
"RESULT: " + NormalizeDouble( deltaVALUE, Digits ) + "|^|",
fsize,
"Courier New",
Yellow // can be deltaVALUE specific too :o)
);
}
if ( deltaVALUE < 0 ){
ObjectSetText( "TimeLabel11",
"RESULT: " + NormalizeDouble( deltaVALUE, Digits ) + "|v|",
fsize,
"Courier New",
Cyan // can be deltaVALUE specific too :o)
);
}
A few remarks on precision of float numbers
You may notice a use of NormalizeDouble()
This is rather important step, to avoid problems with comparison of floats.
If the precision of standard floats ( MQL4 double ) is not sufficient, you may opt-in to use extended precision numbers in MQL4. Check documentation for that.
However, always be carefull on float comparisons.
Best practice, to be on a safer side, is to use both NormalizeDouble() ( as a prevention )
and
comparing to some thresholdDELTA like if ( MathAbs( floatA - floatB ) < anEqualityTresholdDELTA ){ ... } rather than if ( floatA == floatB ) {...}